cheap orbital insertion

Ed,

>
> The length of the accelerator (d), the (average) acceleration (a),
> and the muzzle velocity (v sub f) are related by the following
> equation:
>
> 2
> V = 2 * a * d
> f
>

Yes, I'm familiar with the equations.

>
> The maximum allowable acceleration and the maximum desired orbit
> limit the minimum length of the accelerator. If acceleration of
> human cargo to escape velocity is desired, the maximum allowable
> acceleration would be 3g's, and the minimum length of 2400 kilometers.
>
> If you want to launch straight cargo at 20g acceleration into low
> earth orbit, you only need 150 km of accelerator.
>

I'm also aware of the effects of changing the the G loading.

>
> 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.

>
> With conventional launch systems, you have several drawbacks:
> - explosive rocket fuel that must be processed, stored, pumped, etc
> in specially made facilities, and eventually ignited
> - takeoff in most cases at sea level, through the thickest layers of
> the atmosphere
> - excess weight that must be lifted to near-orbital speeds before
> being discarded (like the shuttle external fuel tank), or re-used
> like the shuttle solid boosters. Large numbers of people and ships
> are required to salvage the boosters.
>

True and I think we need something better but not necessarily bigger.

>
> 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.

>
> > 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.

>
> - 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.

>
> > 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.

>
> > 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?

>
> > 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

Ed,

The length of the accelerator (d), the (average) acceleration (a),
and the muzzle velocity (v sub f) are related by the following
equation:
2
V = 2 * a * d
f

Yes, I'm familiar with the equations.

The maximum allowable acceleration and the maximum desired orbit
limit the minimum length of the accelerator. If accelerationof
human cargo to escape velocity is desired, the maximum allowable
acceleration would be 3g's, and the minimum length of 2400 kilometers.
If you want to launch straight cargo at 20g acceleration into low
earth orbit, you only need 150 km of accelerator.

I'm also aware of the effects of changing the the G loading.

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 howyou use it and what your efficiency is. The energy needed tobring a one kilo mass from 0 to whatever speed you want and the power neededto raise the same mass 300 Kms against gravity is not the same as whatyou use to put the same mass into orbit. That will change dependingon 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.

With conventional launch systems, you have several drawbacks:
- explosive rocket fuel that must be processed, stored, pumped,etc
in specially made facilities, and eventually ignited
- takeoff in most cases at sea level, through the thickest layersof
the atmosphere
- excess weight that must be lifted to near-orbital speeds before
being discarded (like the shuttle external fuel tank), or re-used
like the shuttle solid boosters. Large numbers of peopleand ships
are required to salvage the boosters.

True and I think we need something better but not necessarily bigger.

With a mass driver, the fuel is electricity, taken off the samepower
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 canbe 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 groundas well.

> 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 thatneed to
be covered are:
Why do it the hard way if you don't have to? Hard for itsown sake is not a virtue.

- physics and engineering design: if these aren't done right, nothing
else happens.
- sound business decisions: the US space program is divided upamong
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 andTexas were
up for the launch site. When Texas didn't get it, the complainedand
got Mission Control. Only California makes any sense, asthe 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 thenthere is the problem of environmental impact and other political concerns.

> It is very simple to say that the
> government of the day could just compulsorily acquire it butgiven
> the number of people involved to would be giving the opposition
> political fuel for years. Then there is the environmentalproblems
> 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. Externaltanks
aren't cheap either, yet they get wasted every flight.

Not easy but the government didn't need to take that much of the countryto do it.

> 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 lookingat
> 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 intothe
> big problems.
>
The "other things that take over" you mention are what I am talking
about. Start with a maglev track to overcome static frictionand
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 eitherside,
and if they are placed closely together the effect is an
electromagnetic tube. At supersonic speeds, the combinationof
aerodynamic lift and momentum keep the craft flying between widely-
spaced rings. The payload recieves a final electromagneticpush at
the end of the railgun; perhaps a small rocket engine could boostthe
craft to a higher speed, thus shortening the railgun somewhat.

Just how far apart are these rings of yours?

> A few articles by Tim Beardsley, staff writer for Scientific
> American The first one has a bit on Light Craft in it andis 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 orbeauty or
a
> system or even just how much you would love to ride on one isnever
> going to make it happen but there are people currently workingon
> ways to make it easier to get to orbit and once there you arehalf
> 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 tobuild, even if the magnetic launch was better, that doesn't mean it willbe the way it happens, not the perfect way but that's life.

Darren Brown