Inverse of a solar sail

On 4/9/2022 10:57 AM, Anthony William Sloman wrote:
> On Saturday, April 9, 2022 at 10:06:32 PM UTC+10, Martin Brown wrote:
>> On 09/04/2022 00:33, Carl wrote:
> 
> <snip>
> 
>> OTOH reflecting a photon that has been fired at the vehicle from an
>> external source gives you double the momentum.
> 
> The idea has made it into hard science fiction.
> 
> https://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye
> 
> A laser-driven interstellar craft is one of the plot devices. Not a human-crewed spaceship - human beings have discovered an even better (if somewhat less plausible) plot device for getting around in interstellar space - but Larry Niven does spell out the physics. Jerry Pournelle did the right-wing politics, which is as dumb as you'd expect in American science fiction, but the book was a good read (back in 1974) and sold well.
> 
> <snip>
> 

They also wrote a book called "Lucifer's Hammer" that I read a number of 
year back, it was 1/3rd about a comet impact and 2/3rds about a race 
war. It seemed dumb even for the 1970s.

<https://snarkypenguin.wordpress.com/2017/09/13/r-i-p-to-a-right-wing-ass-dr-jerry-pournelle/>

On Sunday, April 10, 2022 at 3:04:17 AM UTC+10, bitrex wrote:
> On 4/9/2022 10:57 AM, Anthony William Sloman wrote: 
> > On Saturday, April 9, 2022 at 10:06:32 PM UTC+10, Martin Brown wrote: 
> >> On 09/04/2022 00:33, Carl wrote: 
> > 
> > <snip> 
> > 
> >> OTOH reflecting a photon that has been fired at the vehicle from an 
> >> external source gives you double the momentum. 
> > 
> > The idea has made it into hard science fiction. 
> > 
> > https://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye 
> > 
> > A laser-driven interstellar craft is one of the plot devices. Not a human-crewed spaceship - human beings have discovered an even better (if somewhat less plausible) plot device for getting around in interstellar space - but Larry Niven does spell out the physics. Jerry Pournelle did the right-wing politics, which is as dumb as you'd expect in American science fiction, but the book was a good read (back in 1974) and sold well. 
> > 
> > <snip> 
> >
> They also wrote a book called "Lucifer's Hammer" that I read a number of 
> year back, it was 1/3rd about a comet impact and 2/3rds about a race 
> war. It seemed dumb even for the 1970s. 
> 
> <https://snarkypenguin.wordpress.com/2017/09/13/r-i-p-to-a-right-wing-ass-dr-jerry-pournelle/>

It was one more end-of-the-world science fiction novel. The politics was straight Pournelle and even dumber than usual. The "race war" was incidental. It was more about preserving as much of a technological civilisation as possible after a catastrophe.  Apparently it started off throwing in an alien invasion but Jim Baen got them to chuck that out, and that part of the story got recycled in the novel "Footfall" which was even more thick-eared. 

-- 
Bill Sloman, Sydney