henry@utzoo.UUCP (Henry Spencer) (01/23/86)
In the recent joint issue of Communications of the ACM and IEEE Computer
(Nov 1985, both) appears a paper on the search for extraterrestrial
intelligence (SETI): "Signal Processing in SETI", by D.K. Cullers,
Ivan R. Linscott, and Bernard M. Oliver, of NASA Ames, Stanford, and
Hewlett-Packard respectively. By and large it's pretty good, and worth
reading, which is half the reason why I bring it up.
The other reason is one paragraph of incredible nonsense, near the
beginning:
At present spacecraft speeds (circa 1e-4 c), a round-trip to
the nearest star would take about 80,000 years. At 0.32c the
trip could be made in 30 years, but even with a 100 percent
efficient drive, the energy required is the annihilation
energy, mc^2, of the payload. For a thousand-ton ship, this
is enough to supply all US energy needs for a millenium. The
extreme cost of interstellar travel, even with no technological
limitations save those imposed by natural law, probably explains
"their" absence here and casts grave doubt on our ever reaching
the stars ourselves...
This is either political propaganda -- which I had thought beneath such
eminent authors in a technical publication -- or appalling ignorance.
The numbers are probably correct (I have not checked them, but they sound
about right), but the conclusions drawn from them are total bullshit.
An hour's browse through back Interstellar Studies issues of JBIS, or ten
minutes' inspection of the Project Daedalus report, or attending just one
of Robert Forward's talks on advanced propulsion, would reveal this at once.
"All US energy needs for a millenium", at *what* demand? Today's demand?
1940's demand? 985 AD's demand? If it's 1940's demand, then the total
energy requirement is *one* large modern power plant running for a decade
or so. Hardly an exorbitant investment. Obviously they mean today's demand,
but it is worth emphasizing that the energy resources at our command have
grown TEN-THOUSANDFOLD in less than fifty years. One large modern power
plant, *idling*, puts out more power than the entire US did in 1940. If
this trend, or anything remotely resembling it, continues, then the energy
resources needed for starflight will pose little problem soon.
Furthermore, the authors don't seem to appreciate the power levels involved
in even today's primitive rocketry. A single Space Shuttle Main Engine puts
out 5-7 gigawatts of power. A Saturn V at takeoff was FORTY gigawatts of
useful output -- over a tenth of the entire power production of the US.
Handling enormous energies is nothing new in space propulsion.
Robert Forward, who has studied the matter professionally as a USAF
consultant on advanced space propulsion, says that antimatter propulsion
is within our reach with today's technology. Antimatter production would
be extremely expensive, but you don't need much. At $50M/mg (yes, that's
millions per milligram), antimatter is competitive with Earth-launched
hydrogen/oxygen mix for in-space propulsion. At $20M/mg, it's competitive
with fission rockets. At $10M/mg, it's competitive with fusion rockets.
Forward indicated that at least the first of these numbers, and possibly
all three, look possible with current accelerator technology. Antimatter
handling needs work, but doesn't appear to need breakthroughs. (Really
large-scale production would be simpler and safer in space, mind you.)
And if we are on the brink of starflight -- reading JBIS will tell you
that there are *dozens* of different schemes for interstellar propulsion
that look viable -- what about civilizations millenia older than ours?
"Their" absence here is a considerable mystery, which has occasioned much
debate in recent years, but the "extreme cost" of interstellar travel just
does not suffice as an explanation.
"Antimatter rockets will take us to the stars. *This is no longer
science fiction*." -- Forward
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henrygsmith@brahms.BERKELEY.EDU (Gene Ward Smith) (02/10/86)
In article <6315@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >Robert Forward,who has studied the matter [starflight] professionally as a USAF >consultant on advanced space propulsion, says that antimatter propulsion >is within our reach with today's technology. Antimatter production would I must confess to a very considerable lack of knowledge about star travel. But this posting brought to mind a book I read recently, "The Flight of the Dragonfly" I think it was called. It was by Robert Forward, and it featured aliens with vast mathematical abilities. Apparantly, Forward had the idea when writing this book that he knew something about mathematics, and nobody told him differently. The result was my nomination for the funniest sf novel since "The Butterfly Kid". Gag me with a functor! I thought I would die laughing. Anyway, I was wondering, does someone out there know enough about this to tell the rest of us if Forward is talking through his hat again (it kind of sounds like it to me, but as I say, I really don't know) or does he know what he is talking about (this time). >"Their" absence here is a considerable mystery, which has occasioned much >debate in recent years, but the "extreme cost" of interstellar travel just >does not suffice as an explanation. Maybe "they" are a long way away? >"Antimatter rockets will take us to the stars. *This is no longer >science fiction*." -- Forward Thank God it's not science fiction -- that way it stands a chance of being true. :-} ucbvax!brahms!gsmith Gene Ward Smith/UCB Math Dept/Berkeley CA 94720 ucbvax!weyl!gsmith "When Ubizmo talks, people listen."
crm@duke.UUCP (Charlie Martin) (02/11/86)
DOCTOR Robert Forward, whose Ph. D. is in Physics and who has done considerable and worthwhile basic research, CERTAINLY knows *something* about mathematics. Probably more than any 990 other people out of a thousand. But I suppose he didn't realize that the new incarnation of Gauss would be grading his fiction. -- Charlie Martin (...mcnc!duke!crm)
cipher@mmm.UUCP (Andre Guirard) (02/13/86)
In article <11783@ucbvax.BERKELEY.EDU> gsmith@brahms.UUCP (Gene Ward Smith) writes: >In article <6315@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >>"Their" absence here is a considerable mystery, which has occasioned much >>debate in recent years, but the "extreme cost" of interstellar travel just >>does not suffice as an explanation. > > Maybe "they" are a long way away? Maybe "they" don't know we're here. Maybe "they" don't care. Maybe "they" _are_ here, and they're not interfering because they're running a betting pool on how long it will be before the nuclear holocaust. There have been stranger forms of entertainment. Actually if I were "they," I would certainly think twice before helping as belligerent and irresponsible a species as ours is into interstellar space... -- /''`\ Andre Guirard ([]-[]) High Weasel \ x / speak no evil ihnp4!mmm!cipher `-'