# Re: My Two Bits Ain't Worth 1E-15 (Take 2)

```

----------
From: T.L.G.vanderLinden
To: Brian Mansur
Subject: Re: My Two Bits Ain't Worth 1E-15 (Take 2)
Date: Wednesday, February 28, 1996 9:23PM

Hi Brian,

>I first like to say something to you, I'm having troubles reading your
>messages, I am not sure if it is because English is not my native language
>or that it is your writing. Anyway I have the feeling that sometimes you
>letters, I think). So before I can understand what you are talking about,
>I've need to read a certain part several times. I'm not sure if others have
>a similar problem, but would it be possible to write some things more
clear?

Sorry.  Most of the time that I am writing my e-mail's I have serious time
pressure to study for a test or go do homework.  I often don't have time to
proofread to see if I make sense.  Of course I could just sit on them a day
or to, then go back and see if I make sense to myself.

On the e-mail you discussed, I don't think you received an e-mail previous
to it.  That may be a fault with our school computer mailing server or
somehow even my own fault.  Don't worry, it was a bad idea that I was
sending and thats why I wrote the e-mail that you got.  It might have
answered your question as to why we would first shoot the RM out of the back
of Asimov only to catch it again.

The whole idea was to find a way to cut down on the weight of the ship as it
tries to decelerate near TC.  My first idea to solve this problem from a
while back was tankers.  That divided the maximum mass of the ship for the
deceleration phase by however many tankers were used.  By spreading out the
fuel along a track, we are left with only the dry ship mass to slow down
(plus fuel to power the ion accelerator and ionizing lasers for the incoming
RM).

of the Asimov.  It could either carry many, many tons of RM and a rail
launcher to lay the deceleration track or it could hold particle beams (or
masers) to hit a sail that would slow the Asimov.

Jumping to a tangent, I wonder if this idea could help solve some problems
of decelerating Kevin's MARS.  I noticed that his design is launched by
using a beam that hits a sail.  The trouble seemed to be how to reverse the
beam's direction to in order slow the ship.

The solution we've dissused to date is to harnessing that previously
reflected power to run an ion accelerator that speeds its RM up to such a
high velocity that very little RM is needed to stop the ship (compared to
fusion powered ion rocket that can only carry so much power in fusion fuel).

Now about reversing the direction of the maser energy without having
complicating the design.  I wonder if we would be able to build and launch a
massive maser starship that simply harnesses the maser energy from Sol and
redirects it to the side of the Asimov facing TC.

Why would we want to do this since such a design would lose A LOT of power
in the redirection process, not to mension the fact that launching 1E7
masers plus an antenna to get power from the masers back at earth would cost
even more power?

You might not to believe what I'm going to say but I'll say it anyway.  We
DON'T want to use the design I just described (it took me the entire time I
was writing this e-mail to figure that out for myself.  Do I feel dumb or
what?) .  We could much more easily launch more reaction mass with the
Asimov for its ion acclerator than launch 1E7 masers plus a really huge
antenna.  So why bother sending you the previous  five paragraph's?  Because
maybe we can't build an ion rocket small enough and light enough to carry
and still have it give .75c+ exhaust velocities.  Maybe we'll be stuck with
reflecting energy and so I'd like to leave that idea on the board if it
comes to that.

One last tangent.  Some concerns I've had with Kevin's design is how to rig
a stable sail while keeping the Asimov hab and drive modules from being
fried.

The best idea I can come up with is to rig the sail like an umbrella.  While
reflecting the maser beams, it pulls the Asimov hab module along like an
open umbrella pulls a man on a windy day.  I seem to recall that Kevin
adressed the shielding of the hab section by putting it front of the sail.
From an engineering standpoint (like I know anything about egineering),
this seems more difficult than tying cable from the rim of the sail to the
hab section and just letting the sail tow it along.  Do you know what the
group decided on this topic?  Couldn't we just put more shielding on the
side of the hab section facing Sol?

At last, returning from my tangents, I'd like to say that I also may not
make sense because I am just realizing how little I really understand the
designs we've been discusing.  I found out after rereading several
newsletters that I didn't understand Kevin's Mars idea even half as well as
I thought and so I've sent Kevin and Kelly some questions.  I'll  give you a
copy just in case you have time to answer a few.

Since you answered most of my questions about my two bits worth, I'll I can
clear up the final paragraph that you didn't get.

>>Since we'll have to carry so much reaction mass for the launch track, I
>>suggest we use the E18W we have planned to mag-sail launch the ship.   So
I
>>guess we launch the track via the ion accelerator using it as a rail gun
if
>>that is possible.

>This part is an example of the kind of thing where I don't get what you
want
>to say even after reading it several times.

In the first sentence I was trying to take into account how the heck we
would push a ship that is carrying all of the RM needed for a deceleration.
Essentially my idea was to use a beam (maser, laser, particle beam,
whatever works) to push what was probably going to be a multi-million ton
starship.

The mag-sail propelled by a relativistic particle beam has been my prefered
idea only because I think I understand the concept.  Not a very good reason
for supporting it but now I know how congress and the public feel when faced
with the choice of new technologies to invest time and money into
researching, producing, and using.

By the way, I found out last night that a Kevin's MARS idea seemed to be
using another kind of sail to reflect microwaves.  If this statement is
incorrect, please correct me.  I wander in the dark here.

The second sentence of that admittantly confusing paragraph (two sentences
does not make a paragraph I seem to remember my 8th grade english teacher
saying) seemed to be a fragment referring to how to save ship mass by seeing
whether or not we could have the ion accelerator double as rail gun launcher
for the reaction mass rather than carry a separate rail gun in addition to
the accelerator.