[ExI] Brake lights

[Rafal Smigrodzki]

On Sat, Jan 15, 2022 at 2:52 AM BillK via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> On Sat, 15 Jan 2022 at 10:10, Rafal Smigrodzki via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
> >
> > I keep thinking about how to decelerate a starship at the destination
> star system enough to allow orbital insertion. Obviously, the amount of
> energy needed to decelerate a payload will be almost identical to the
> energy needed for acceleration but deceleration is likely to be much harder
> than acceleration to achieve technically.
> >
> > Let's assume we want to move the smallest payload sufficient to start a
> colonization process at a destination star. This would be probably a few
> grams of self-replicating machinery (nanotech or highly modified
> biotechnology) capable of photosynthesis in an abiotic planetary
> environment, and capable of then bootstrapping radio antennas and the
> computational substrate to receive the colonist minds beamed from the
> origin star system.
> >
> > The most promising technology to accelerate this kind of payload is
> laser powered light-sail. One interesting implementation of this idea are
> small lasers powered by solar arrays that would coordinate to produce
> massive terawatt beams. These would not have a single origin but rather
> originate from a swarm distributed over the whole solar system. In this way
> the extreme acceleration of the payload could be sustained over a long
> stretch as the payload traverses the laser swarm and receives continuous
> boost from the swarm elements that are closest to it at the time. This
> would be much better than a single giant laser that could accelerate
> payload only for a shorter period of time.
> >
> <snip>
> > --
> > Rafal Smigrodzki, MD-PhD
> > Schuyler Biotech PLLC
> > _______________________________________________
>
>
> You are describing the ‘Breakthrough Starshot’ project.
> <https://breakthroughinitiatives.org/initiative/3>
>

### No, the Breakthrough Starshot does not mention laser arrays distributed
over the whole solar system and does not consider options for deceleration
at destination.
-------------------------------

>
> This idea has just been reviewed (and the problems listed) by an
> astro-physicist.
> <
> https://medium.com/starts-with-a-bang/ask-ethan-could-the-breakthrough-starshot-project-even-survive-its-planned-journey-6f307fdb1aa9
> >
>
> As with all space travel enthusiasts, he reaches the conclusion that
> the problems are probably unsurmountable, but we should try anyway.
>

### He is making assumptions about the transfer of energy between dust
particles and the starcraft and pulling numbers out of thin air. Also, dumb
assumptions about the rest of the mission parameters, like target speed and
duration. A billion years is a long time, so a wide range of starcraft
speeds can be explored during colonization, and the slowest speeds that
still allow interstellar spread throughout the galaxy over tens or hundreds
of millions of years are *definitively* achievable using existing or
readily conceivable technologies.
 ---------------------

>
> There is a big difference between solving problems in PowerPoint and
> virtual reality and actually getting things to work in the harsh
> environment of the real world.


### There is a big difference between rigorously pointing out physical
limitations and making up just-so stories to fit a preconceived conclusion.

Rafal
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