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starship-design: Local Gas Density

Looks like I missed my fuss! Anyway, it could have been a good one. I see
some snippets quoted from posts I missed over the weekend that I lost my
ISP, that I'll have to read in next quarter's archive. Like:
>Did I miss something? I thought the local interstellar medium had been
>determined to be thinner than once thought - like only 0.1 atom per cubic

Yup, recent supernova in the area cleaned out the area.  The formal name is
something lige a local bubble or something.


Have you missed something? Priscella C. Frisch of the University of Chicago
opined back in 1994 that we just entered an interstellar gas cloud. "Using
cosmic-ray data and stellar spectra gathered by seven satellites...
According to Frisch, until just a few thousand years ago, the solar system
was cruising through interstellar space that was almost devoid of matter.
Then, perhaps within historical times, 2,000-8,000 years ago, the solar
system plunged into an interstellar gas cloud. This cloud is believed to be
the remnant of the bubble of matter shot into space perhaps 250,000 years
ago by a supernova in the Scorpius-Centaurus region."
(Frisch, Priscella C.; "Morphology and Ionization of the Interstellar Cloud
Surrounding the Solar System," Science, 265:1423, 1994. Also: Peterson, I.;
"Finding a Place for the Sun in a Cloud," Science News, 146:148, 1994.)

More recently, Markus Landgraf et al. of ESA, working with the Ulysses probe
which has been orbiting out of the ecliptic for 8 years, confirm the
presence of a gas and dust cloud. 'The best match, they found, was with a
mixture of silicates detected in interstellar clouds elsewhere in the Milky
Way, suggesting that we are moving through an identical cloud. "We were very
excited when we found that the composition fits," says Landgraf. The notion
that we are travelling through an interstellar cloud is not new. First a
cloud of gas was discovered moving through the solar system. Then by 1995,
Ulysses had detected enough galactic dust grains to see that they travel
through the solar system in the same direction as the gas, suggesting that
the cloud consists of dust as well as gas.'

Whether or not a "recent" supernova cleaned out the gas in our area, we
stumbled into a cloud very recently. It's too soon to dismiss ram scoops;
first let's get some hard info on what's really there. If we're in a cloud,
rams will work.

Johnny Thunderbird