Should be working :-)
Agree with much of this, but a few comments.

> The modern 747 has a lot of years on the design.  The only competitor
> nowadays are Airbus proposals that have to run a lot more efficiently to
> even be considered.  Once you break the sound barrier, efficiency drops
> out the floor, so barring a large paradigm shift it will generally be
> cheaper to fly long flights at subsonic speeds than supersonic speeds.

Note that the 747 flies very very very close to the speed of sound. A close
to optimum solution to the large volume transportation subsonic design.

>Where's that bullet train?

19 years ago I rode it at 230 kph between Tokyo and Kyoto. No toy either - a
very large train and a mainstay of commercial service. Peaked at about 230
kph. Fastest I've been on land.

> Personal automobiles all go 70MPH in the US for safety reasons

That's actually a design decision. In Germany recently on the autobahns we
would sit on about 130 kph (80+ mph) in the slow lane. People would
frequently pass us at upwards of 220 kph (140 mph) (based on stopwatch
measurements I made) and a few were faster. (At 130 kph some people were
passing us at a closing speed of more than the NZ 100 kph speed limit). We
saw very few accidents and those seemed to be of "lesser" vehicles. (When
they do have a decent accident it's a very spectacular one of course). The
Autobahns were in may cases simple two lane per direction roads with
apparently standard surfaces and normal widths (in places they used a
temporary reduced width 6 foot outer lane - now that's exciting) The two
things that seemed to make these roads VERY fast and apparently much safer
than one may have expected were the very high radius bends and the driving
philosophy. Drive in the slow lane unless overtaking. Leave the fast lane
clear. CLEAR!  If overtaking check behind CAREFULLY, pull out, do it, get
back in, QUICKLY!. Tarry a little at 140 to 150 kph and there's a Mercedes
glued on your rear bumper. No horn, no lights, no aggro - just zero inter
car clearance until you pull over and let them go on their way. Pfffft.
Gone.

>On the racetrack, exponential growth in racing speeds leveled off 50 or 60
years
> ago.

I think that to some extent that also is a "design" decision - accidents got
too dangerous and they have limited engine size and capability allowed for
many years. (No turbos, no ground effect skirts). Also tightened up track
rules (chicanes) to limit peak possible speeds. But still we would not have
seen exponential speed increases.

> Yes we can build a rocket sled that Yeager could break the sound
> barrier with, but what use is it?

I understand that the japanes are trialling a new high speed service between
Tokyo and the Narita airport (1 hour+ by road). About 500 kph I think. Very
small driverless automated tracked vehicles. Sounds like fun. Still well
below the speed of sound.

> Space has hit a similar crisis.  We thought we would use the moon as a
> stepping stone to explore Mars, however the costs and risks are
> exponentially higher in a Mars mission and the benefits don't look too
> good.  Earth orbit satelites have exploded commercially, but nobody sees
> enough economic benefits in the Moon as of yet, let alone other
> destinations, to try for commercial apps.  Heck, commercial spaceflight
> for live astronauts is not even off the ground yet, with several teams
> competing for the prize.

There never was a compelling commercial motivation wit a paybacvk period
short enough to justify commercial investment. There are quicker ways to
make your millions and ones that need smaller entry level capital. The 60's
space race was politically driven. Thankfully :-) - or we wouldn't have evn
got to where we did. That will change. But before it does we will be back on
apolitically motivated son-of-space-race but on the cheap to 'dominate cis
lunar space, which is where this thread srtarted. The political threat is
the slowly advancing ESa, the incipient Indian efforts and the leaping ahead
Chinese efforts. The Us scannot afford 9they feel) to let China achieve
mastery in this arena. So we'll be going back to the Moon just as sooner as
the Chinese do ;-)

Sooner or later, if the recent thread on energy futures is to be believed,
we'll be going back into space for economic reasons. Lunar Helium 3 promises
to solve our next few energy crises (jusdt as soons ass we work out how to
keep it inside its (magnetic?) bottle while it does it. And orbiting power
satellites may yet prove viable as situations change.


> The Moore's law expansion of silicon technology is going to level off, and
> soon.

Never be sure of this :-).
Physical size may asymptote, but new twists may keep the 2^(2N/3) increase
in functional capabilities alive for some while yet. Look for quantum
computing on your desktop within the decade.

> The computer on my desk at work is a 1.6 GHz P4 model, the one at home is
> 200mHz P2, and I literally cannot tell the difference in performance.  Why
> upgrade?

For many applications that's true. But for such a mundane task as
manipulating my (44,000!) trip photos, processor and disk speed is proving a
major bottleneck. I need about ten times as much processing power as I'm
prepared to pay for :-)

> Do you remember the performance difference between a 25 MHz 386
> and a 100 MHz 486?

Yes!


        Russell McMahon

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