RE: SETI Microprobes and Interstellar Travel

Clements, Robert (
Thu, 9 Sep 1999 12:12:43 +1000

There are a bunch of ways of beating the challenges of extraterrestrial
flight with robotic probes; & no doubt we'll use all of them... possibly in
the not-too-distant future (before the current budget chaos, Dan Goldin was
on record as expecting a probe into interstellar space - which may or may
not be the same thing as an interstellar probe - as likely to be launched
within 40yrs... if M2P2 propulsion (potentially: a fine cost/speed
compromise for exHeliopause research) really stacks up, this estimate might
actually be conservative. Comets may not be the ideal solution, though... or
@ least: not in the manner you describe: too slow; & the system actually
gets slower the further you are from the Sun.

What comets _are_ is a fine, flying resource base, rich in water &
carbonaceous compounds (presumably, there are also metalrich asteroids out
in interstellar space; but this comment remains highly speculative); & their
value for interstellar colonists - if not their robotic predecessors - will
be considerable. What's the cheapest way to build a space colony fleet?
Essentially, you _don't_ build it; but start carving them out of the insides
of large, metalrich NEOs. Launch a small fleet of them towards the target
star before any of the colony ship are completely built, with a skeleton
crew on each (you might be talking about leaving with less than 10% of final
capacity prepared); & your colony has the freedom to expand through the dark
light years of space; collecting consumables from comets as they fly. If
there _are_ metalrich asteroids en route; these, too, could be redirected
towards the target star; & added to the fleet. Given that you're carving
from the inside rather building from the outside, the walls could be safely
thick to avoid particle damage @ low relativistic speeds; & it might even be
possible to generate electromagnetic fields around the ship to charge &
deflect particles headed towards the ship.

All highly speculative, of course; but a wonderfully messy alternative to
gleaming Star Trek....

All the best,
Robert Clements <>

> -----Original Message-----
> From: Richard Burke-Ward []
> Sent: Thursday, September 09, 1999 2:04 am
> To: SETI League
> Cc: Allen Tough
> Subject: SETI Microprobes and Interstellar Travel
> Dear all,
> First up, where is everybody? Is it just me that is getting maybe one
> posting from this list every other day, or has the list just gone quiet?
> I suspect I'm badly behind the times, because I only ever got David
> Woolley's reply to Allen Tough's reply to something or other on the above
> issue, but none of the original messages... So if I am repeating
> something, then do forgive.
> Interstellar microprobes need not travel unprotected at even
> sub-relativistic speeds. How about if they hitch rides with comets? It
> would be the interstellar equivalent of Tarzan swinging from tree to
> tree. Get a ride to the outskirts of system A, jump to a comet on the
> outskirts of system B, nudge it out of the belt and into the system, drop
> a few probes in system B as you pass through, then jump ship in favour of
> a comet which can take you into system C... It may not get you to every
> solar system in the galaxy, but it would get you to a lot of them. Nice
> and slow, nice and protected, with an almost limitless source of raw
> materials for self-replication / sub-probe creation.
> David, I know you were not arguing interstellar microprobes were
> impossible, just that there were technical challenges involved. This is
> true. However, I think arguments such as yours are too often seen by
> others as 'proof' that probes are impossible. So it is worth just setting
> out again some of the reasoning.
> Probes might be self-replicating, or launched as a fleet. Either way,
> let's be miserably pessimistic and say that it would take a wave of
> probes 100 million years to saturate the galaxy. That is 100th the age of
> our galaxy. I truly find it hard to imagine that, in roughly 10 billion
> years, with a few hundred billion stars to choose from, that no single
> instance of intelligent life has had such an idea and at least partially
> implemented it. (OK, let's assume you need second generation stars, plus
> intelligent life takes 4 billion years to evolve - so make that 4 billion
> years.) It follows that there is at least a chance we could find evidence
> of extraterrestrial intelligence *within the confines of our solar
> system*.
> Arguments against looking for such evidence seem weak. There are the
> technical ones - we don't know interstellar travel is possible, etc.
> Well, NASA seems to think it is - even with technology only a hundred
> years or so beyond present day - plus we've had at least one meteorite
> land on Earth which originated in another solar system - plus we are
> talking about ETI's with technologies considerably in advance of our own.
> Interstellar travel is probably difficult (so is space flight, so is
> building a computer) - but to rule out interstellar travel as impossible
> when we cannot possibly *know* it is impossible seems very foolish. The
> other argument against looking for probes in our solar system really
> comes down to ignoring the problem and hoping it will go away - 'give us
> a good search stgrategy and maybe we'll think about it...' Several people
> have been offering good ideas for years - Allen Tough among them. And
> more to the point, if people don't like the ideas that have been
> suggested, why not *help* us design good ideas? The important thing is to
> recognise the *need*.
> I personally find it haunting in the extreme to think that I may be
> sitting within a few AU of absolute proof that ETI exists. It may not be
> a functioning probe, it may just be a relic - even the equivalent of a
> flag planted millions of years ago... If someone told you that there was
> a 50% chance that something like AC Clarke's obelisk really *was* sitting
> on the moon (or in orbit, or on an asteroid), would you just ignore the
> possibility? Effectively, that's what's happening. That chance is very
> real indeed - and no one seems to want to do a thing about it.
> This isn't cranky. This is an attempt to define a new branch of SETI. One
> with a real chance of success.
> Not everyone can do everything. The SETI League is a radio-based
> organisation. But its members are not solely interested in radio, they
> are also interested in ETI. Plus they (you all) are deeply creative,
> innovative, and have the courage to think new thoughts. If any new
> initiative in the area of searching for probes were to start, the grass
> roots of the SETI League would be a wonderful place for it to happen.
> If anyone is interested in throwing ideas around, I would love to talk
> with you. I know Allen - and a few others - would too. You might also
> want to have a look at a mathematical treatment of the problem on my
> website - I try to quantify the chances that there is something here
> worth looking for - (some of you have already
> looked and commented - thanks).
> Richard

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