Solar sails and mission structure

[Nick Tosh <101765.2200@compuserve.com>]

Hello again everybody.

Sorry I'm so slow to contribute, but I'm very busy working for my A-levels
- British equivilent of American high school graduation, only harder ;) and
preparing for an admissions interview for Cambridge University (British
equivilent of Harvard, only... no I'm not gonna say that). I'm afraid I'll
be a bit out of phase with everyone else for a while.

Thanks everyone for the mailing list info, I've just sent my subscription
mail. It doesn't send everything as one big mail does it? It's just that my
family's getting a bit fed up of finding 70 odd mail messages for me every
week!

Kelly wrote about my solar sail post:

>The stellar radiation would be too breif and weak to help us much.

I know it wouldn't be much good for a multimillion ton Asimov, but I had in
mind a light interstellar shuttle to ferry personel and light supplies
between the target star system and Earth, for which a solar sail might
provide helpful additional breaking, especially at highish velocity, maybe
passing the target star completely and reversing back, with the sail furled
of course (and using gravity to help) - see my last mail. (By the way,
Timothy, thanks for telling me that I can either count the photons OR
calculate the Doppler shift. I knew that particle and wave mechanics have
to be kept separate, so I'm not sure why I was being stupid. Always glad to
have you to correct me!) This really links in to my ideas on the mission
structure that I mailed to LIT just before I went off line (must be about a
year ago now). I've dug it out and pasted it below. Is anyone still
interested in mission structure? I don't recall we ever reached a complete
agreement. Please let me know your reactions to this concept.

Posted: 4 October 1995

>I've got a few points to make about the general structure of the mission.
>
>        Firstly, the mission should make future journeys to TC more
feasable - this
>would require the setting up of a small but expandable permanent presence
on
>one of the terrestrial planets. The ultimate aim would be for the TC
'colony'
>to be effectively self-supporting. The mistakes of the Appollo program
must be
>avoided - it will be essential to maintain the momentum of the program,
since
>the other alternative would probably be a general loss of intrest and a
set
>back of manned interstellar travel.
>       Secondly, I've always felt that using the Asimov to bring the crew
home is an
>inefficient solution. The Asimov is designed to be a heavy exploration
vessel,
>not a ferry. Once it has delivered its huge payload of machinery and
material
>to TC, using it to transport a relatively few number of people back to
Earth is
>somewhat ridiculous.
>       I would propose a fairly radical change to the mission plan.
>        - The Asimov should be designed as a one way vehicle for
exploration. Its
>effectiveness in this role can be maximized if the return flight is no
longer
>an issue.
>        - On arrival in the TC system it would serve as a permanent
space-based
>command, control, and support centre for the develpment projects on the
planet.
>Thus a permanent foothold can be established before planetary construction
is
>even begun.
>        - The construction of a 'colony' would be less frantic if those
involved knew
>that there already existed a safe haven for them in-system.
>        - Two or more dedicated personnel transport vessels, designed
separately from
>the Asimov, should be constructed. They would only have to ferry people
and
>small quantities of light supplies and equipment, and so would have a tiny
>fraction of the mass of the Asimov. It might therefore be possible to
propel
>this type of vessel using solar sail and magsail technology, augmented by
an
>artificial particle beam during the early phase of the flight, and a small
on
>board antimatter engine for maneuvering and possibly as an early boost.
>Ultimately, a two way particle beam between Earth and TC would be
established.
>It is even possible that the Asimov's engines might be used to produce a
beam
>to increase the acceleration of the small transport vessels back to Earth.
>Cetainly it could provide many support functions for the transports (eg
>communication relay, TC based mission control, repair).
>        - These vessels would be used to relieve the crew of the Asimov
with fresh
>people. The round trip (time dilated) for the original crew might be 25-30
>years (some might want to stay longer). With two vessels, a relief ship
might
>arrive in TC every 15 years (TC time)
>
>        If a permanent presence is to be established, it is clear that an
>interstellar shuttle system is needed. Further, it is obvious that a
>prohibitively expensive Asimov type vessel it not appropriate for this
>function. I conclude that if an austere ferry system will have to be built
>eventually, it makes sense to incorporate it into the original mission.
The
>advantages of having the huge Asimov remaining as a planet-orbiting base
in TC
>are obvious.
>
>Please respond with any opinions you might have about what I've said. Do
you
>agree with my basic argument, if not the details?

On another topic, I'm still not happy with the stellar drive system. It
still seems to me (after reading everyone's mails on the subject) that for
it to obey Newton's Third Law, it depends on a particular distribution of
charge around the drive that may (or may not, for all I know, I haven't
looked at this thoroughly) be statistically very probable, but surely isn't
an absolute requirement. So I ask again: does this concept put conservation
of momentum on an equal footing as the laws of thermodynamics (which are
essentially statistical, not absolute)? If it does, either it's very wrong,
or I'll be very, very, unhappy.

Sorry I haven't responded as fully as I'd like to other people's mails, but
I am reading them and  keeping fairly up to date.