Rich Freeman on 3 Mar 2017 07:34:46 -0800

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Re: [PLUG] "Nearby"

On Fri, Mar 3, 2017 at 8:59 AM, Timothy Jones <> wrote:
> Once you reach a certain speed in space, unless you encounter a significant
> dust cloud or gravitational body, you won't slow down. In Earth's atmosphere
> you need constant thrust to compensate for air drag. In space, there is no
> drag force so once you accelerate to a certain speed and then stop firing
> your engines, you may end up going that speed forever and ever... However,
> between the time of their initial engine firings to accelerate fast enough
> to get out of our system, and the time they would need to start reverse
> thrust to obtain orbit around TRAPPIST-1, they wouldn't need to use a single
> drop of fuel except perhaps for occasional short trajectory corrections
> every few thousand years.

Of course.  I was addressing what it would take to get a ship there in
a relatively short duration (in the sense of "The Apollo 11 astronauts
could have been there by now."  That requires almost continuous thrust
to reach very high speeds.

Getting there in the most efficient manner possible is an entirely
different matter.  I'm not entirely convinced that we can build a
probe today that would still be able to return data after thousands of
years, but if we had one we could probably get it over there using
today's technology.

Honestly, though, such a probe would probably arrive to find the
planet inhabited by humans who are celebrating "The First Probe Has
Arrived Day."  These humans might have left Earth 1000 years later
using technologies we can only speculate about, and they would have
decided to not touch the enroute probe just to see if it actually
makes it.  :)

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