🚀 go-pugleaf

In article <1992Oct5.161556.29814@aio.jsc.nasa.gov>, kjenks@gothamcity.jsc.nasa.gov writes:
> I, kjenks@gothamcity.jsc.nasa.gov, wrote:
>>> My ground-based lasers would get you a net thrust, albeit a small,
>>> inefficient one.  But we've got several centuries before we can 
>>> change the atmosphere, anyway.  Lasers are patient.  We can wait.
> 
> In article <1992Oct2.202211.1@fnalc.fnal.gov> higgins@fnalc.fnal.gov (Bill Higgins-- Beam Jockey) writes:
>>Where do you put them?  At the point on the surface where the planet's
>>orbit intersects it.  
> 
> Actually, you can put them anywhere.  If it's not "At the point on the
> surface where the planet's orbit intersects it," you have some
> off-center thrust, but it's still thrust.

I was thinking about the optimal place to do the burn.  Off-center
thrust wastes your effort to some extent (it'll spin up the planet or
whatever)-- but may be more practical.  You would like, of course, to
apply thrust along the tangent to the planet's orbit.  I failed to say
that I was thinking about the *ideal* place to apply thrust.

Most of your remarks are comments about my musings on the ideal case.

> It's all academic, of course.  You need a LOT of lasers (or flashlights
> or radio stations) for a LONG time to budge a planet.  And you have to
> get there to put them in place and coordinate them carefully to get
> the desired effect.

Ken, how much does the Earth's orbit change because of radiation
pressure?  Kilowatt per square meter, albedo 0.4.  I'd do the
calculation but I'm really getting hungry and I want to go home to
dinner.

The Sun must be pushing Venus outward even harder.  How long before
Prof. Abian gets his wish?  Nice physics problem.

Unless your lasers can put a lot more delta-V into the planet per unit
time than the Sun does (and their source of energy must be real
magic!), it doesn't seem worth building them.

> It might make a nifty device in a science fiction story, and 
> entertaining speculation on Usenet, but that's about it.

True... 

>      "NASA turns dreams into realities and makes science fiction
>       into fact" -- Daniel S. Goldin, NASA Administrator

Not *this* dream, I trust.  (I wonder if Goldin would like to come to
a science fiction convention sometime?)

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