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bitrex
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On 8/23/2020 7:40 PM, bitrex wrote:
The fusion ramjet has hardly left the garage at that point that is to
say, it isn\'t even up to cruise speed
On 8/23/2020 7:23 PM, Ricketty C wrote:
On Sunday, August 23, 2020 at 3:39:30 PM UTC-4, bitrex wrote:
On 8/23/2020 3:29 PM, bitrex wrote:
On 8/23/2020 3:25 PM, bitrex wrote:
On 8/23/2020 1:15 PM, Ricketty C wrote:
On Sunday, August 23, 2020 at 8:11:26 AM UTC-4, John S wrote:
On 8/21/2020 8:10 PM, Ricketty C wrote:
On Friday, August 21, 2020 at 3:49:41 PM UTC-4, Pimpom wrote:
On 8/21/2020 10:54 PM, Ricketty C wrote:
On Friday, August 21, 2020 at 11:55:30 AM UTC-4, bitrex wrote:
On 8/21/2020 6:38 AM, Phil Allison wrote:
Hi,
Recently it has become normal for astronomers to directly
observe planets around nearby stars in an optical telescope.
Couple of months ago, they found two in circular orbit around a
very new star.
https://www.businessinsider.com.au/first-ever-photo-shows-2-planets-orbiting-sun-like-star-2020-7?r=US&IR=T
Seems there are in fact billions of the damn things.
Be \"... an awful waste of space \" if Earth is the only one
with life forms.
Above quote from the SF movie \"Contact\".
..... Phil
I\'m probably remembering the exact figures incorrectly but if
you could
push a space telescope out to about a tenth of a light-year from
Earth,
it could leverage gravitational lensing to make an equivalent
lens of
enormous size.
It could then search for evidence of life in a large volume of
space by
imaging planetary surfaces around other star systems directly,
it could
resolve stuff like oceans, plants, or structures.
But the time required to return those images would be...
astronomical.
Sending back digital images over a distance of a tenth of a light
year by radio wave would take, well, just one-tenth of a year, or
about five weeks. No problem.
The big problem is to reach that 0.1 light year distance first.
The farthest man-made objects are now travelling at ~15 km/s
(Wikipedia). At that speed, it would take over 2000 years. :-(
You misunderstand. I\'m referring to the RF link analysis. They
have a very hard time seeing anything other than stars because
other objects are too dim. I haven\'t done the math, but the data
rate would have to be microscopic to successfully send and receive
a radio signal from such distances. 0.1 light year is 6324 AUs.
The Voyager probes are about 141 AU so about 40 times closer. They
now are transmitting at 160 bps. Doing the math I get about 3
years to transmit a MB of data.
? 10Mb/160bps = 62.5k seconds = 17.4 hours. What am I doing wrong?
Not as bad as I thought, but I suppose they would highly value any
image compression, but lossless of course. With the image mostly
the star, I suppose they could do a fair bit of compression.
Still, they would want to transmit and awful lot of MB, so it will
take lots of time, still years.
Imagine what it would take to manage the cameras and other devices.
Over a month just to send any message no matter how short.
160 bps is what they have now, not from 0.1 light years away. Apply
the -17 dB factor and recalculate... I think the distance ratio is
actually 45. Opps, I think I made a mistake. It should be -33 dB,
no? I used 10log instead of 20log. So yeah, years.
I suppose they could just pop in a power source 2,000 times more
powerful. How many kW would that be? Or is it MW? Not MW, they are
currently using 23 watt transmitters, so 45 kW instead, only slightly
less than WWVB. Can we launch WWVB into space?
You\'d use a laser of some type, probably. One megawatt laser through
40 meter optics should be at least detectable by similar optics up to
20,000 light-years away:
https://iopscience.iop.org/article/10.3847/1538-4357/aae380
At a thousand AU you\'d need more than 25 watts, but likely not
megawatts. I don\'t think a radioisotope-thermal source would cut it
but small fission reactor might work.
Optical nuclear-electric battery seems like a plausible power source,
better power-to-weight than radioisotope thermal, less complexity than
something with circulating coolant
https://en.wikipedia.org/wiki/Optoelectric_nuclear_battery#:~:text=An%20opto%2Delectric%20nuclear%20battery,constituting%20a%20%22dust%20plasma%22.
Or you could just have the whole power-generation system on Earth for a
relatively (heh) short distance like that. A huge-ass 100 megawatt laser
beams power to the spacecraft\'s solar panels and uses the electric power
to run its ion drive to accelerate it up and slow it down, and at 1000
AU there\'s enough received power from the huge-ass laser on Earth to run
a downlink laser back. Flight time would be about 20 years
What speed could be achieved? 1000 AU is still 6 times closer than
0.1 light year.
When I first typed up my post I overstated the distance to get a
gravitational-lens effect off the Sun\'s own gravity well. 500-1000 AU
should be enough. Nuclear thermal rocket, specific impulse ~1000 seconds
could do 1000 AU with basically current technology well within a human
lifetime. Ion/plasma drive, specific impulse 50,000 seconds, cuts it
down to 10 years maybe.
To go faster than in reasonable time that you need something far beyond
near-future tech. Fusion ramjet cuts it down to 3 months or so I think,
but you might as well send it on to the nearest star at that speed.
The fusion ramjet has hardly left the garage at that point that is to
say, it isn\'t even up to cruise speed
\"to go faster\" will do fine