Re: I think we forgot to ask this

In article <1140951637.440333.259490@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
rja.carnegie@xxxxxxxxxx <rja.carnegie@xxxxxxxxxx> wrote:

James Nicoll wrote:
During the discussion of the Heimian FTL drive last month:

Given a crewed ship* with the mission duration of a nuclear
sub, a reliable FTL** speed of 50 C and enough delta vee than
landing and taking off (not to mention matching velocity with
the target system), where would you want to go?

www.stellar-database.com may be useful.

I wonder how many of us are actually qualfied to play... but do you
have in mind colonisation, scientific study, or tourism?

I think it's more interesting to leave it open, to see
what criteria people come up with on their own.


Lessee... 50 C gets us to Proxima in about a month, and so on. I guess
that just about works for a pleasure cruise, if the shipboard
entertainments are good enough in between. But you kind of want to get
your feet on the ground when you arrive in port - or in orbit.

Proxima is an interesting star, because it's a flare star.
Every once in a while, it unloads about 4x10^21 watts in x-rays
long enough to release 1.5x10^25 joules in total. ISTR it takes
about 200 Joules to deliver an LD50 lethal dose of radiation, so
assuming a human has about a square meter of surface area, this
would kill about half the people exposed in a ship 77 million
km from the star. A hypothetical habitable planet would be about
a million kilometers from Proxima.

An atmosphere like ours would block the x-rays but I think
ships would want serious shielding.



* Uncrewed probes seem likely to have useful ranges many times higher
than crewed ships. Voyager is, what, 30 years old? And since the
FTL speed could be double or more for ships you never need to slow
down, they might reach as far as 3000 ly before crapping out. That
might include as many as a quarter of a billion stars.

Actually, there's a second question: where would you send
the long range uncrewed probes?

Can we make the centre of the galaxy? There's interesting stuff
happening there.

Even if we use Van Maanen's Star and an Oberth manuever,
plus doubling the speed because the probe will never slow down,
the best speed we could hit might be something like 245 C. The
center of the galaxy is about 30,000 ly or over a century. I'd say
no chance.

The disk is only 5000 ly thick: a few decades would get
the probe well about it, with a less impeded view of the center.

Actually, if we could find a quiet neutron star, they have
escape velocities of about half the speed of light. If you built
a very durable probe and did a 2000 km/s Oberth down where the
V(esc) was 100,000 km/s, you should get a delta vee of 20,000 km/s
and that translates into 1000 C. That gets you to the center in
a generation and a half.

Unfortunately, the nearest known neutron star is
RX J185635-3754, which is about 200 light years away (or
four years at 50 C). The good news is that it is headed this
way at a good clip.The bad news is that the environment
near a neutron star may be excessively interesting.

If the ship doesn't come home, how does it report back?

I have a weak chain of logic to think EMR has to propagate
in hyperspace, because if it doesn't, anyone travelling there has
more serious problems than not being able to phone home. If it
does, it should enjoy the same x15,000 multiplier other speeds
do.

--
http://www.cic.gc.ca/english/immigrate/
http://www.livejournal.com/users/james_nicoll
.

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