Probe to A Centauri

Assume for the sake of argument that we discover an earth mass planet
in the A or B Centauri system. Further assume spectroscopic analysis
detects copious water, O2, N2, and methane in its atmosphere. Further
assume that it becomes possible with 2-3X Apollo effort to send a
2000Kg probe at .1 c there.

Now, what do we include on this probe to measure things that we will
not be able to measure from our solar system given 45 yr advances in
technology? In other words, given the very long flight time, some
instruments might be made outmoded by advances in remote sensing
capabilities.

In article ,
Parallax wrote:
...assume that it becomes possible with 2-3X Apollo effort to send a
2000Kg probe at .1 c there.
Now, what do we include on this probe to measure things that we will
not be able to measure from our solar system given 45 yr advances in
technology?

Actually, the first problem is to decide whether a probe launched 20 years
later will arrive earlier. It makes little sense to launch a starprobe
until the rate at which projected trip time is shrinking with
technological advances goes below 1 yr/yr.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Parallax wrote:
Assume for the sake of argument that we discover an earth mass planet
in the A or B Centauri system. Further assume spectroscopic analysis
detects copious water, O2, N2, and methane in its atmosphere. Further
assume that it becomes possible with 2-3X Apollo effort to send a
2000Kg probe at .1 c there.

If this was the case (interstellar probe for teh effort of 2-3x apollo)
there would be a probe on its way towards the centauri anyways.


Now, what do we include on this probe to measure things that we will
not be able to measure from our solar system given 45 yr advances in
technology? In other words, given the very long flight time, some
instruments might be made outmoded by advances in remote sensing
capabilities.

At .1c, teh flight time is not that long. Telescopes are quite old
instruments by now and are unlikely to go out of vogue. Same
approximately applies to other instruments.

--
Sander

+++ Out of cheese error +++

"Henry Spencer" wrote in message
...
In article ,
Parallax wrote:
...assume that it becomes possible with 2-3X Apollo effort to send a
2000Kg probe at .1 c there.

These are really, really, really optimistic assumptions for a long, long
time. It is hard to come up with technically plausible schemes to reach .01
c at any cost, much less the 100 times more costly (in energy) .1 c

Now, what do we include on this probe to measure things that we will
not be able to measure from our solar system given 45 yr advances in
technology?

Actually, the first problem is to decide whether a probe launched 20 years
later will arrive earlier. It makes little sense to launch a starprobe
until the rate at which projected trip time is shrinking with
technological advances goes below 1 yr/yr.

In fact it makes little sense to send a probe until remote sensing
capabilities have reached their practical limit. The immediate tradeoff is
between spending the vast sums needed for a probe on extraordinary remote
data collection schemes which operate at 1.0 c and are also reusable against
other targets.

But the principal issues in an interstellar probe is that is going to be
performing a very high speed fly-by. It will be using remote sensing
equipment much like Earth would use, but could get much closer, but for very
short periods of time. Thinking about it this way makes the tradeoff with
stay-at-home sensor systems even clearer. For 1/10000 of its flight time it
is 10,000 times closer than Earth sensors are, but with sensors of vastly
smaller apertures. Stay-at-home sensors can collect data over very long
periods of time.

A probe gains additional advantage for its closeness with active sensing
systems since their performance scales with the inverse fourth power of
range instead of inverse squared, but they are far more costly to operate.
Still, a radar mapping system might be the most valuable thng a probe could
carry.

A unique observation mode that only a probe could carry out is having a
chunk of probe hit the planet's atmosphere and collect data on the effects,
which no doubt could reveal some things about its compostion and structure
that purely passive observations could not.

You would probably send twin probes together in one package, BTW. This
allows closest approach fly-bys on opposite sides of the planet and provides
insurance against complete mission failure due to the very unlikely but
probably catastrophic impact with a meteoroid.

Carey Sublette

Let's keep it in this galaxy for the time being since it is 100,000 light
years across it.
The next galaxy if out of the question. I think I read that Voyager 1 will
reach the next galaxy in 30 thousand years or so. The dinosaurs could be
back before then.

"Parallax" wrote in message
om...
Assume for the sake of argument that we discover an earth mass planet
in the A or B Centauri system. Further assume spectroscopic analysis
detects copious water, O2, N2, and methane in its atmosphere. Further
assume that it becomes possible with 2-3X Apollo effort to send a
2000Kg probe at .1 c there.

Now, what do we include on this probe to measure things that we will
not be able to measure from our solar system given 45 yr advances in
technology? In other words, given the very long flight time, some
instruments might be made outmoded by advances in remote sensing
capabilities.


---
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(Henry Spencer) wrote in message ...

Actually, the first problem is to decide whether a probe launched 20 years
later will arrive earlier. It makes little sense to launch a starprobe
until the rate at which projected trip time is shrinking with
technological advances goes below 1 yr/yr.

For once I must disagree with you, at least if the probe also sends
back data before the Alpha Centauri encounter.

If it don't, then of course you are right, but IIRC only the Ranger
6-9 opperated under these conditions, as the extra experiments had
given trouble during Ranger 1 - 5, and consequently managment desided
that no. 6-9 would do the pictures, and *nothing* else. So that there
wouldn't be any problems with interference from magnetometres or
*anything* other than the cameras.

The data from Voyager was better than Pioneer 10, but those from
Pioneer 10 came first.

The Voyagers has overtaken the Pioneers, but they all have given back
data on the space between Earth and heliopause.

As long as you also collect data along the way, I'd say that two
probes see more than one.

And the probe you have already launched cannot be proxmired in the
next budget - always a consideration in space flight.

Regards

Carsten Nielsen
Denmark

Rodney Kelp wrote:

Let's keep it in this galaxy for the time being since it is 100,000 light
years across it.
The next galaxy if out of the question. I think I read that Voyager 1 will
reach the next galaxy in 30 thousand years or so. The dinosaurs could be
back before then.

Um, assuming it was even headed for Alpha Centauri, Voyager wouldn't
reach the next *star* by then, much less galaxy....

(Unless you were headed for Andromeda [M31] at about 7.5 times the
speed of light, anyway.)


--

You know what to remove, to reply....

In article .net,
"Carey Sublette" wrote:

...an interstellar probe is...performing a very high speed fly-by...
A unique observation mode that only a probe could carry out is having a
chunk of probe hit the planet's atmosphere and collect data...

This seems a very careless and possibly disastrous plan.
What would be the ground effect of an object moving at
an appreciable fraction of C, grazing the atmosphere of Earth?

Considerable heat and other radiation - forest fires,
sonic overpressure sufficient to shatter structures - and
if by some small error, it should impact the surface?

If there was intelligent life below such a fly-by, would
it be able to recognize it as a "probe" and not an "attack"?

Rodney Kelp wrote:
Let's keep it in this galaxy for the time being since it is 100,000 light
years across it.
The next galaxy if out of the question. I think I read that Voyager 1 will
reach the next galaxy in 30 thousand years or so. The dinosaurs could be
back before then.


Voyager can't possibly get to the next galaxy in 30000 years - maybe you
meant the next star system? But Voyager is not really a good yardstick
to measure things by - if we launched a deliberate interstellar probe now
it would make it there much faster. But really - for now the timelines are
far too long for it to make sense.

--
Sander

+++ Out of cheese error +++

Carsten Nielsen wrote:
(Henry Spencer) wrote in message ...

Actually, the first problem is to decide whether a probe launched 20 years
later will arrive earlier. It makes little sense to launch a starprobe
until the rate at which projected trip time is shrinking with
technological advances goes below 1 yr/yr.

For once I must disagree with you, at least if the probe also sends
back data before the Alpha Centauri encounter.

If it don't, then of course you are right, but IIRC only the Ranger
6-9 opperated under these conditions, as the extra experiments had
given trouble during Ranger 1 - 5, and consequently managment desided
that no. 6-9 would do the pictures, and *nothing* else. So that there
wouldn't be any problems with interference from magnetometres or
*anything* other than the cameras.

The data from Voyager was better than Pioneer 10, but those from
Pioneer 10 came first.

The Voyagers has overtaken the Pioneers, but they all have given back
data on the space between Earth and heliopause.

But these were not deliberate interstellar probes, simply probes that
headed off into interstellar space after the main mission was accomplished.
The problem is that the probe you can make in 5 years - as opposed to now -
would probably catch up the other well before Neptune's orbit.

Just imagine there was financing available for probe that went as far
possible as fast possible with non need (or permission) to share
payload for any secondary goals - up to and including substituing
fuel for electric propoulsion (or not having that weight) for doing
something "useful" during planetary fly-bys. If it was chemistry -
or some other subject thats funded :P - thats what you would do. Build
the fastest, sleakest most capable probe you can and get it past heliopause
on the shortest course.


Regards

Carsten Nielsen
Denmark

--
Sander

+++ Out of cheese error +++