Re: Serious propulsion

From: Marc 182 (marc182spamless_at_globalcrossing.net)
Date: 02/22/05 

To: sci-space-tech@moderators.isc.org
Date:  Tue, 22 Feb 2005 02:15:14 -0700

In article <GemdnRZS1cWOOoXfRVn-2g@look.ca>, earlcp@idirect.com says...
> schillin@spock.usc.edu (John Schilling) :
>
> > alexterrell@yahoo.com writes:
> >
> > >Henry Spencer wrote:
> > >> In article <1108143123.041040.288750@g14g2000cwa.googlegroups.com>,
> > >> <alexterrell@yahoo.com> wrote:
> > >> >> the problem is not the solar cells but the structural dynamics of
> > >> >> enormous lightweight solar arrays...
> > >> >> ...Solving either in the next 20 years is conceivable, but not
> > >> >> a small project...
> >
> > >> >But if you have lots of ion thruster, you can have lots of solar
> > >> >arrays, each flying independently, powered by four ion thrusters.
> >
> > >> If they're connected by cables or structural elements, they are *not*
> > >> flying independently, and the dynamics problems have *not* gone away.
> > >>
> >
> > >As long as the electrical cable is not taut, they are flying in
> > >formation, but exerting no force on each other.
> >
> >
> > The electric cable can only be "not taut", if the cable is massless
> > and/or the spacraft are not accelerating. Otherwise, the cable is
> > under at least enough tension to supply the force accelerating the
> > mass of the cable. While that force may be small, if the other
> > part of your system is a swarm of middling large but featherweight
> > gossamer structures, it's enough. Henry is right, this is a Hard
> > Problem. Almost certainly harder than making one huge solar array,
> > and that's not easy.
> >
> > There may be some merit to a swarm of modestly sized flying solar
> > arrays using *beamed* power transfer, whether microwave or laser,
> > and I have seen the idea proposed here and there. But it also is
> > rather beyond the state of the art.
>
> Don't forget to add in the problem if one of the thrusters fails. With a
> large array of thrusters (100+) it would be silly to shut the rest down as
> the loss of one thruster would make very little diffirence the flight
> profile. But that thruster and it's array will for sure start tensioning the
> cables.

Obviously you provide a way to cut-away a failed array. Was that too
much alliteration for a science newsgroup?

Marc

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