Re: starship-design: Interstellar mission within fifty years

[Zenon Kulpa <zkulpa@zmit1.ippt.gov.pl>]

> From: KellySt@aol.com
> 
> In a message dated 10/13/98 11:23:59 AM, zkulpa@zmit1.ippt.gov.pl wrote:
> 
> >> From: KellySt@aol.com
> >> 
> >> In a message dated 10/9/98 9:01:44 AM, zkulpa@zmit1.ippt.gov.pl wrote:
> >> 
> >> >I don't think so. Controlling sustained fusion reaction
> >> >and directing the output to achieve efficient thrust
> >> >still wait for breaktroughs.
> >> 
> >> We don't actually need sustained, 
> >>
> >Eh? Do you thing that micro-explosions or similar concept
> >may lead to a viable starship engine? 
> 
> Sure, we use micro explosion to power most of our suyrface transports.  No
> fundemental reason a pulsed fusion drive is out of the question. At a high
> enough pulse rate all the pulses just form a vibration load, which is
> handelable.
> 
> >I doubt it.
> 
> Why?
> 
Not because of the word "explosions", but because of the word "micro".
For a starship, you need rather macro-explosions (and the big 
"macro" for that). For macro-explosions it will be next to impossible
to reduce pulsing to mere "vibration load".


> >I must disagree. Of course funding is necessary,
> >but all currents concepts how to built it I know about
> >seem to me to be blind alleys - maybe possible as a laboratory
> >experiment, but impractical or impossible to scale up
> >into the terawatt-range needed for a starship.
> 
> The Bussard designs I used seemed pretty scaleable, the laser 
> fusion systems looked good.  Natural since we never built 
> a production copy this is questionable, but for a 50 year timetable 
> it seems reasonable.  Its not like
> I'm pitching zero-point energy systems or something.
> 
OK, but still it is only handwaving at this stage, you must admit.


[...]
> >> >Not speaking about the waste heat (again - question 
> >> >of efficiency, but not only).
> >> 
> >> Irrelavent.  The waste heat would be dumped into a area of space 
> >> after The power was converted from sunlight.  Average heat load 
> >> in the area wouldn't change much.
> >> 
> >Just "dumped"? Into what "area"? 
> >In space you can expel the waste heat by radiation
> >only, and for terawatt-range power stations that means huge 
> >high-temperature radiators and efficient enough heat transfer
> >from the concentrated "reaction chamber" (or lasering medium)
> >into that huge radiating structure... 
> >Above some power threshold it may become simply impossible. 
> 
> Or a hugh number of gigawatt platforms (current SSPS designs) 
> scatterd over a 1 AU ring.  
> 
I know, I know, thousands of Chevrolets linked together... 


[..]
> >> >Like the space elevator - theoretically possible, and
> >> >we have even produced an appropriate material (buckytubes).
> >> >Do you think we will build such an elevator within 50 years?
> >> 
> >> I doubt we will ever build one. They cost far more then they are worth.
> >> 
> >I do not speak about the cost, but about the technological
> >(and manufacturing...) ability to actually build it,
> >provided we have the money.
> 
> Well we could build one now out of Kevlar and metal if we were 
> crazy enough to write the checks to cover the STAGERING costs of it.
> 
No, kevlar + metal is not strong enough. Buckytubes are (barely).
I still do not see technological & manufacturing ability
to build it now, no matter how big check you can underwrite...
And the starship is much more hard to build, in my opinion.


> >> Agree that Apoll made a lot of sence as a cold war "battle", 
> >> but a historian from 1919 would have found it pretty implausible.
> >>
> >I do not think so. There are plenty of examples in history when
> >political reasons lead to great technological advances.
> >I think that it is true for MOST of civilization advances...
> 
> But most look pretty unbeleavable ahead of time.
> 
Huh? Possibly as concerns the particulars, but the rule
itself is well-known since some time...

-- Zenon