Coil guns vs. mass drivers

--- In spacesettlers@egroups.com, "bill t" wrote:
>
> I would love to see the length being wrong.
>
> The problems you mentioned for Australia are also true for Canada.
> Transportation in Canadian Praries might be slightly better, but its
> not the interstate system the U.S has.
>
> It may not be as big a political nightmare here, because the area is
> mostly private property, but is very sparsely populated.
>
> In reality it becomes a question of how much is space based
technology
> worth to the planet?
>
> Bill
>

Bill,

A very unexpected change to my timetable, completely ruining
everything I've set-up for the next week, not that they care, has
given me the chance to look at my books and numbers and I've got good
news and bad news.

First the bad news, due to declining mental faculties, failing
eyesight, overwork and general stress, environmental factors and
other external events beyond my control, as well as a decimal point
that jumped into the wrong place, all by itself (well that's my story
and I'm sticking to it). I'm forced to admit that 1500 Kms is only
1.5 million metres not 15 million (sound of a person muttering under
his breath, while looking at the ground and shifting his feet in an
embarrassed manner) but the rest of the calculations were right or so
my text books tell me. Now the good news, your length is still not
quite right, in a way. I'm uploading an Excel spreadsheet to give
you the basic numbers (a very quick and dirty sheet so don't expect
bells and whistles). If you are going to get a load up to escape
velocity, ~11 Kms/sec then you will need a launch system only 12,124
Kms long, not 1500, not much of a gain really. Better news is why
that fast? All you really need is to get to orbit and then you can
use low thrust/ high impulse engines to get you higher or even
tethers or some other way, in that case you only need a launch unit,
say 350 Kms long. Still big but much better than 1500 Kms. Which
brings up a point, why use it at all? I read the rest of your upload
and it changes a few things. These are in no particular order;

Given that you are really looking at an end of the world situation
then any objections about environmental damage are nonsense. That
being the case you are thinking much too small and at the same time
too big. Why take so many people? Certainly you don't want to leave
anybody behind but given the time line you are looking at most of the
population today will be dead before anything happen so if you had
good population control you would only have to move a fraction of the
people you first had. This is also a problem for you as a lot of
people will not want to work to solve a problem that isn't going to
happen until after they and their children are gone, they will try to
put it off to later.

Next you will need a lot of infrastructure in space to do this and
fast, so I'd be going over and digging out the plans for Orion. The
Australian desert would be just about perfect for building and
launching something like old bang-bang and it would just about put a
fully built and working base into orbit. Fallout, I hear you say, so
what, soon it is going to a lot hotter than that.

Massive mining of the solar system will give you all the raw
materials you need so you shouldn't need to lift from deep gravity
wells. That just leaves people to get from Earth. I'd be using a
large Lightcraft and it's cousin that uses microwaves from orbit.
Also do you need to take the whole person or just the eggs and
sperm. Move as many people as you can and then germ plasm from as
many others as possible to give you the maximum genetic variation.

Bottom line, if you are evacuating then why bother to use a launch
system as clean as a coil gun, you're not coming back and what is
left is soon going to be toast, do whatever it takes.

Of course if you are not in that situation you might want to consider
looking at laser launch systems for people and maybe
magnet/chemical/plasma launch for cargo that isn't so fragile.

Darren