cheap orbital insertion

--- In spacesettlers@egroups.com, Darren Brown wrote:
>
> Ed,
>
> > Yes, I'm familiar with the equations.
> > I'm also aware of the effects of changing the the G loading.
>

Sorry, my caffeine system had too much blood in it, and I was cranky.

>
> > The Physics are the same whether you use a stage rocket like the
> > Saturn V, or a composite structure like the Space Shuttle, or an
> > electromagnetic gun. The Energy requirements are the same.
> >
> No, here you are wrong. The energy needed is related to how you
use it
> and what your efficiency is. The energy needed to bring a one kilo
> mass from 0 to whatever speed you want and the power needed to
raise the
> same mass 300 Kms against gravity is not the same as what you use
to put
> the same mass into orbit. That will change depending on just how
you do
> it, none of the machines I've ever seen are 100% efficient, not all
> systems are equal, except in a physics classroom.
>

The current launch trajectory of the space shuttle is highly
inefficient. Instead for direct orbital insertion, they go to about
98% of the speed required, drop down, release the fuel tank so that
it falls into the Indian Ocean, and then pick up speed again. If
they carried the fuel tank into orbit with them, it would take LESS
fuel!

By the way, NASA will launch the external tank for free, if you can
retreive it, make sure the rapid decay of the insulation coating
doesn't rain anywhere near existing sattelites or the shuttle itself,
and move it into a stable orbit. That's 30 tonnes of space-rated
Aluminum alloy, shaped as two tanks both space-rated at over 1
atmosphere of pressure, with hatches at each end, and an intertank
structure containing a beam strong enough to carry the entire
load of the solid rocket boosters, and a strongback capable of
sustaining the entire load of both boosters and the main engines. If
they go for direct orbital insertion, the tanks would contain about
1000 kg of leftover Hydrogen and 10000 kg of leftover Oxygen - very
valuable property for free, if you can get it. How's that for cheap
orbital insertion?

Even if they go for direct orbital insertion, the space shuttle must
climb directly through the thickest layer of atmosphere, since they
start at sea level. The first 3000 feet is the thickest.

> >
> > With a mass driver, the fuel is electricity, taken off the same
power
> > grid as your computer. It all stays on the ground. So does your
> > propulsion system, which can be maintained directly from ground
> > bases. All you launch is payload. Launch systems can be
automated,
> > enabling multiple daily launches. It is all based on existing
> > technology.
> >
> With a lightcraft the fuel, motor and all the heavy parts stay on
the
> ground as well.
>

Agreed, and the lightcraft is an idea well worth considering. It
does have the advantage over a railgun of a small footprint.

>
> > > My problem with such large systems is that
> > > while they make great settings for a story, they have practical,
> > > logistical problems that are very hard to solve, an example is
> > > problem of just acquiring the land to build the thing, you will
> > need
> > > both public and private land.
> >
> > What did Kennedy say in his we will go to the moon speech? "We go
> > there not because it is easy, but because it is hard." ... or
> > something like that. The practical, logistical problems that
need to
> > be covered are:
>
> Why do it the hard way if you don't have to? Hard for its own sake
is
> not a virtue.
>

I'm not necessarily saying pick the hardest way possible, far from
it. The hardest way possible is the way we are using right now, with
chemical and liquid rockets.

However, just because there are technical problems, doesn't
necessarily mean that they are insurmountable.

> >
> > - physics and engineering design: if these aren't done right,
nothing
> > else happens.
> > - sound business decisions: the US space program is divided up
among
> > several states; launch facilities in Florida, Mission Control in
> > Texas, and landing facilities in California, for instance. The
> > reasons for this are largely political. Both Florida and Texas
were
> > up for the launch site. When Texas didn't get it, the complained
and
> > got Mission Control. Only California makes any sense, as the
landing
> > strip is perfect.
> > -public acceptace of the new mode of travel: sure to come quickly
> > when a trip into space is as cheap as a trip across the continent.
> >
> You have left out the need to get the land to build the thing and
then
> there is the problem of environmental impact and other political
> concerns.
>

You're right, I did. OK, environmental impact first. This can be
divided up into several categories:
- environmental destruction due to building the project. Most of the
sites that would be suitable for building a railgun (or a lightcraft,
for that matter) would have areas where it would not be convenient to
build a road. A mountain peak that had a fairly level summit might
have sheer cliffs all around. Much of the construction equipment and
parts might need to be transported by heavy-lift helicopter. There
are some fragile ecosystems to consider, and certain mountaintops are
sacred to native peoples. But there are many, many routes to
consider if we are looking at routes of less than 200km. How many
marshlands were paved over to build Kennedy Space Center? How many
fragile desert ecosystems have gone extinct due to Edwards Air Force
Base? Has it made a difference? Has anyone noticed?
- atmospheric pollution due to system operation: clearly, the
conventional rockets are the big losers here. With
electromagnetic launch, it is as clean as the system which generated
it (coal, nuclear, hydroelectric, solar, etc).
- noise pollution: again, conventional rockets are the big loser
here. There is a sonic shock wave in either case: along the railgun
the shock wave is broken by the shape of the solenoid rings. There
is no such baffle for rockets. They also produce a noise from their
controlled explosions that literally shakes the earth.

Now, political considerations. If the railgun needs to be less than
160 km long to be effective, there are a huge number of sites around
the world that are potential candidates. Turkey is such a
mountainous country, there are several places within it that could be
used as launcher sites, in several different directions. Australia
possesses a large meteor crater in the middle of the Northern
Territory, and the south rim (near Alice Springs) looks attractive;
most of its launch trajectory would be in a roughly polar orbit, over
the Pacific. Australia also has a nice, long mountain range in
northeast Queensland and another along the coast of New South Wales.
Columbia may own day become known for more than coffee and cocaine;
the mountains on its west coast offer particularly attractive
trajectories. There are tons of sites available, with trajectories
that do not cross over other political jurisdictions.
Probably the biggest political consideration is: what if there is an
accident? What if it fails? The US space program was not prepared
for Challenger; the political fallout cost NASA years of lost time.
If a lightcraft were to suffer a catastrophic loss of power, the
craft would plummet (not designed to glide). If a railgun were to
suffer loss of power to one of its rings, it would probably still
function; if there were a catastrophic loss of power, it would depend
on the position of the projectile within the gun. Near the beginning
(while still on the maglev track) would probably not lead to
catastrophe. The first few kilometers of the railgun assembly would
probably be the most dangerous, where the rings are placed close
together; catastrophic loss of power would likely mean a crash, and
the partial or complete destruction of several rings. Near the end
of the railgun, momentum and lift would likely be enough to keep the
projectile going to an emergency landing strip. The worst-case
scenario is not as bad as the Challenger disaster: it is easier to
mass-produce solenoid rings than it is to build a new space shuttle.

>
> > > It is very simple to say that the
> > > government of the day could just compulsorily acquire it but
given
> > > the number of people involved to would be giving the opposition
> > > political fuel for years. Then there is the environmental
problems
> > > and while people may think they would be small or non-existent,
> > just
> > > showing that is a major headache, then there is the cost and
> > > maintenance.
> >
> > It is not easy to maintain a conventional launch system, either.
It
> > costs a lot of money to keep the Shuttle fleet going. External
tanks
> > aren't cheap either, yet they get wasted every flight.
> >
> Not easy but the government didn't need to take that much of the
country
> to do it.
>

In terms of total area, the US space program takes up a larger
footprint than my proposal. A strip 1km wide by 160 km long is
equivalent to a 10km/16km military base; the Kennedy Space center is
comparable in area.

>
> > > Big projects such as a magnetic launch system may one
> > > day happen but I think I will be betting on other methods
killing
> > it,
> > > with the possible exception of the maglev system NASA is
looking at
> > > but that is just a way to start and get moving, then other
things
> > > take over, being just a few kilometres long it doesn't run into
the
> > > big problems.
> > >
> > The "other things that take over" you mention are what I am
talking
> > about. Start with a maglev track to overcome static friction and
> > build up some speed, then the solenoids take over, pulling the
> > payload in and pushing it out the other side to the next solenoid;
> > the solenoid's EM influence extends for some distance on either
side,
> > and if they are placed closely together the effect is an
> > electromagnetic tube. At supersonic speeds, the combination of
> > aerodynamic lift and momentum keep the craft flying between
widely-
> > spaced rings. The payload recieves a final electromagnetic push
at
> > the end of the railgun; perhaps a small rocket engine could boost
the
> > craft to a higher speed, thus shortening the railgun somewhat.
> >
> Just how far apart are these rings of yours?
>

One of these days I am going to have to figure out all the math and
determine the optimum spacing for the rings, their size, etc. Or
perhaps someone else out there has already done the math...

>
> > > A few articles by Tim Beardsley, staff writer for Scientific
> > > American The first one has a bit on Light Craft in it and is
worth
> > > reading, it's under the sub heading "Beam me up".
> > >
> > > Light Craft & others.
> > > http://www.sciam.com/1999/0299issue/0299beardsley.html
> > >
> > > Making Money in Space
> > > http://www.sciam.com/1999/0399space/0399alpert.html
> > >
> > > Trends in Space
> > > http://www.sciam.com/0696issue/0696trends.html
> > >
> > > The Future in space
> > > http://www.sciam.com/1999/0399space/0399quicksummary.html
> > >
> > > Summary of articles
> > > http://www.sciam.com/1999/0299issue/0299quicksummary.html
> > >
> > > Just a couple of things to think about. The elegance or beauty
or
> > a
> > > system or even just how much you would love to ride on one is
never
> > > going to make it happen but there are people currently working
on
> > > ways to make it easier to get to orbit and once there you are
half
> > > way home.
> > >
> > I have read all the articles you mention, and I have studied
> > extensively on the subject; I started my university education in
> > astrophysics.
> >
> > At least we are agreed on the need for easier ways to get to
orbit.
> > I have yet to do a full analysis of the costs of such a project,
but
> > I estimate that it would be somewhere in the range of the Space
> > Shuttle program; ie NASA's total annual budget for three years.
> >
> > :) ed
> >
> I have no idea of the cost, just the thought that they may be
easier to
> build, even if the magnetic launch was better, that doesn't mean it
will
> be the way it happens, not the perfect way but that's life.
>
> Darren Brown

You're right. No government will build it unless it is politically
expedient. No private citizen or corporation would build it unless
it would turn a profit - which it would. Wish I had Bill Gates'
money!

:) ed