Robber Barons in Space

> > An orbital tether system, some means of storing fuel, and better
> > yet, refining fuel, also providing orbitally obtained life
support
> > materials. This is akin to laying down the roads or wagon
trails,
> > having watering stops for the mules, having some nice vittles
for
> > the travellers and a place to rest for the weary folk as they
> > journey into the desert for their own reasons.
>
> Can you explain more about a "tether system"? Is this the "space
> elevator" I hear about or just a means of connecting two otherwise
> diparate space contraptions together to form a "unified" system?

No, it's not the space elevator system. An elevator would be
attached to a point on the earth and extend out into space, with its
center of mass at geostationary orbit. This is a huge undertaking
and requires materials to withstand impressive tensile loads. We
don't have those materials in the engineering toolbox, although
people point to lab samples of nanotubes and feel comfortable
extrapolating their engineering use. I think many things can go
wrong between a 1 gram lab sample and millions of tons of the stuff
making a tower 35,000+ kilometers long.

For a more detailed fictional account of this techology read Arthur
C. Clarke's "Fountains of Paradise."

The problems I mentioned for constructing such a device on Earth are
not present in a lower gravity environment such as the Moon, Mars,
or Mercury. The tensile loads are lower and thus are within reach of
existing materials. Hans Moravic did a nice analysis of the
requirements for a lunar elevator.

http://www.frc.ri.cmu.edu/~hpm/project.archive/1976.skyhook/papers/sc
asci.txt

A space tether system, OTOH doesn't attach to the planet and doesn't
face the same tensile stresses. By my reckoning there are two
families of space tethers: 1.) skyhooks and 2.) rotating tethers.
FWIW, I prefer the rotating tether system.

A skyhook would consist of six primary components. At the lowest
altitude would be the docking station. At the highest altitude would
be another station, let's call it the launching station. Midway
between the two is the midway station. Joining all stations is a
cable system. Attached to the cables are the elevators. And finally,
attached to the midway station are the PV cells that power the whole
endeavor.

This skyhook will be orbiting the earth and its orbit will be
determined by its center of mass - the midway station. Because the
skyhook will be gravity gradient stabilized, or tidally locked, it
will always maintain the same orientation towards the Earth.
Further, the upper and lower stations, if unattached, would have
different orbital velocities. But they are attached, so the orbital
velocities of the two stations are the same as that of midway
station. The implications of this are that the lower station has a
lower orbital velocity that it would if it was unattached, and the
upper station has a higher orbital velocity.

Let me switch gears for a moment. Using the rocket equation, you can
get more bang for your buck if you launch a suborbital payload
rather than one destined for a higher orbit. Further, you don't need
to engineer as sophisticated (nor as expensive) a rocket to reach
suborbital velocity. You can probably build a suborbital shuttle
that has a high payload capacity to fuel capacity ratio.

Now by combining these two principles you can launch the payload in
your suborbital shuttle or ELV and dock with the lower skyhook
station, which is in orbit, but is orbiting at a velocity less
than "orbital velocity." If the whole skyhook structure is
engineered properly, you can even dock the shuttle to the structure
and it will orbit the earth indefinitely.

Now the payload is transferred to the elevator cars and using $10.00
worth of electricity the payload is lifted to either midway station,
where the orbital velocity is equalized, or it is lifted to the high
station where it can be launched with an added velocity boost
because the high station, moving at the same velocity as midway
station, is moving faster than it needs to be in order to maintain
orbit.

While this structure wouldn't be permanently attached to the surface
of the earth and be 36,000 + km, it would still be quite long by
terrestrial engineering standards.

Keep in mind that the greater the distance between the low and high
stations, the lower the docking velocity and the higher the boost
gained from launching from high station. Also keep in mind that the
lower station probably shouldn't go below 150 km in order to avoid
atmospheric drag.

Thus, if the rough orbital velocity at 150 km, itself an unstable
orbit, is 7.8 km/s, and you had a cable length of 746.9 km from the
lower station to midway, and 800.8 km from midway to high station,
then your docking velocity would be only 85% of orbital velocity.
Further if you launched from the high station, then you would be at
about 88% of escape velocity for that altitude. You'd still need
some rocket assist, but not as much.

If you increase the length of the cables seperating the stations,
then you also increase the length or the orbital period, so you
can't launch as frequently from the same spaceport. But to offset
this supposed disadvantage, you make other gains. Consider, a lower
cable length of 1751.5 km and an upper cable length of 2,050 km. Now
the docking velocity is only 70% of orbital velocity and your launch
velocity is now 99% of escape velocity.

Not too bad! But first you need to build the damn thing and as
you've probably noticed, there is a trade-off between lower shuttle
performance/increased paylod ratio against the size of skyhook
apparatus.

Now let me pontificate about a rotating tether system.

It works on the same principles as the skyhook, but because it
rotates it really amplifies the momentum exchange properties. Let's
put this is real world terms. You're at a skating rink and all your
buddies join hand in hand to form a chain. You can join the chain
and climb along by pulling yourself (skyhook elevator) and not use
any leg power (rockets) or you can hang on as they round the corner
and whip you along and watch you zoom by at the release point
(rotating tether.)

With the rotating tether you've got a simpler device, but you're not
docking to a "stationary" point but a docking bay that is rotating.
I don't think that should pose an unsurmountable problem, its just a
matter of matching velocities and timing arrival time.

Once the payload is picked up it is swung about and released. Then
the tether loses some orbital height, just as the skyhook would. But
if the tether catches a payload of equal mass from on high and
lowers it, then its orbit is restored.

How practical is it to count on deorbiting mass to restore the
tether to its original orbit? In the early stages probably not too
practical. We could deorbit some satellites and let the tether take
them the last mile so to speak. That would work towareds restoring
(assuming equal masses) the orbit and the satellites would burn up
in the atmosphere.

But if it's one way traffic we're modeling, and you recall that
there is no such thing as a free lunch, then you'll be saying to
me "Hey, all we're doing is trading reduced fuel for the payload
against the need to reboost the skyhook or rotating tether. How is
that more efficient?"

Well you didn't really think I was going to write this whole long
post and not have an answer for you, did you?

Here's how the efficiency comes about (and I'm discounting for now
the returned payload scenario though I think it will be significant
in the future - see my 60 Easy Steps posts :)

We are transferring the momentum of the large mass tether to the
smaller mass payload and thus increasing the velocity of the payload
disproportionately to its mass and conversely, the tether's velocity
drops and so too does its orbit. For an illustration of this check
out page 8 of this report.

http://www.tethers.com/papers/CislunarAIAAPaper.pdf

You'll recall that the kinetic energy of these object has the mass
proportional to the square of the velocity. Further, while we can't
launch from earth using high ISP ion thrusters, they are perfectly
suitable for orbital work.

It is more efficient to restore the energy lost from the tether
using high ISP engines than it is to boost the payload without a
tether system and having to boost the fuel and the rockets as well.

Further, the tether by lowering a conducting cable into the
atmosphere, and running a current through it can boost itself using
electrodynamic forces. No rocket fuel is needed, just electricity!

For more on this topic check out

http://www.tethers.com

and Vincent Cate's site

http://www.spacetethers.com

I perfer the rotating tether because it is lower mass and simpler to
construct but if traffic increases in orbital space then I would
favor a more elaborate and expensive skyhook system. This opens up
whole new vistas that the rotating tether can't match.

For instance, you could build hotels and crew stations along the
cables. You can have a Mars gravity training facility, hotel, or
theme park at 340 km altitude, where the gravity experienced would
be about 1/3 of Earth's. Do the same for the Moon at the 900 km
level so that 1/6 gravity can be experienced. Make the thing long
enough and the expense of engineering and operating suborbital
shuttles gets much lower, their ticket prices come down, tourist and
commerical traffic increases to the tether. Moreover, this makes
suborbital hops from city to city more cost effective, thus
increasing the number of shuttles and lowering their unit cost, thus
making traffic to the tether even less expensive. Even more
moreover, crews returning from extended zero-g missions can
reacclimate at the "Moon Level" then move down to the "Mars Level"
before they have to land on Earth with its crushing "Earth Level"
gravity.

As an aside, even if an ambitious skyhook is constructed, I still
think you'd need the MEO station and the lunavator that I've
described in the 60 Easy Steps series of posts.

>
> > Now let anyone who can pay the fare go to orbit to make what
they
> > will of their own privately funded ventures. They'll pay for the
> > fuel and life support, and a tax will eventaully recover the
cost
> of
> > the other infrastructure.
>
> I think this is a great idea having government build
infrastructure
> and tax it's use. But I read somewhere that the biggest problem
with
> Gerard K. O'Neill's plan (L5 Colony building SPS systems) was it's
> dependence on government. That dependence was termed "naive" as I
> recall.
>
> I am curious. Your idea (and I have read many of your previous
posts
> as well as enjoyed some rather spirited discussions with you
myself)
> seems to fall under the same category - dependent on government
(tax-
> payer) financing. Are you saying that the illusive space market
> cannot be motivated by the private sector to develop such
> infrastructure? Are we trapped until someone can convince our
> government or the collective governments of the world to develop
this
> infrastructure? Is there any other way in your estimation? Others
> should of course chime in with their opinions as well.

No, I'm not saying that government(s) has to fund the endeavor, but
what I am saying is that it will require a large pool of capital and
a coordinated effort.

Although unlikely, it is not inconceivable that a consortium of
companies can get together and pull it off. By my reckoning they
have to be willing to commit at the minimum $100 billion - $500
billion + dollars to establish a barebones orbital economy. That's a
huge sum!

It makes little economic sense to spend billions developing CATS
when there is little market for launch other than satellites.

It makes makes little economic sense to spend billions developing
lunar mining facilites when there is no one to buy the dirt.

It makes makes little economic sense to spend billions developing
orbital refining facilities when you can't get any dirt or ores, and
there is no one to buy the refined metal.

It makes makes little economic sense to spend billions developing
fabrication facilities when you can't get any raw materials and even
if you could, there was no one to buy the finished good.

It makes makes little economic sense to spend billions developing
means to get volatile gases to support life if there is no one
living in orbit.

It makes makes little economic sense to spend billions developing
orbital fuel refineries if no one wants to buy your fuel.

You get the point. In isolation, none of these economic activities
makes sense, but if developed in concert, then you develop a
marketplace.

The end result is that you need to extract wealth from the Earth's
economy and transfer it to the orbital economy in order to justify
those coordinated investments. The finished product at the end of
the food chain, IMHO, will be SPS energy. I can't see anything else
that makes sense. So until money is flowing from Earth to pay for
that energy, the other suppliers (i.e. miners, refiners,
fabricators, farmers, technicians, etc) will all have to wait in
order to be paid.

In the immediate future, I think government(s) have the best chance
of marshalling the resources. Will they? No, they won't because
there are too many competing demands for the tax dollars.

In the longer term, I do think corporations will do it. In the next
century or so. That's because the amount of capital in the world is
increasing and this is unleashing competitive forces. The
competition will only increase and this will drive down the returns.
Any corporation that finds itself a lucrative market will have
competitors entering that market and reduce it to a place where the
low cost producer survives, ceterus paribus. Beware, long winded
explantion follows :)

The only way to defend the high returns is to erect a barrier to
entry. Technological innovation is one such barrier, so too is the
need for large amounts of capital.

These days, techonological barriers can be circumvented through the
courts and legislation or through copycat innovation. Look at the
pharmaceutical industry. Viagra opens up a whole new market with
very lucrative returns. Companies try to overturn the Viagra patent,
some countries don't honor it, and some corporations, seeing how the
chemistry of the drug works, can now duplicate the result with
unique new chemical formulations that don't violate the Viagra
patent.

Intel didn't use to have as many chip competitors as it does now
because each Fab plant would cost it over a billion dollars.
Nowadays, a billion dollars isn't as significant a hurdle as it was
20 years ago. The cost of capital is cheaper and access to it is
easier.

So what are companies to do if they don't want to battle it out as
low cost producers? Can they ever find a defensible position where
they can earn significant returns?

Yep, you guesses it. Invest in orbit. Access to vast amounts of
capital is easier these days, but not so easy that one can put
together a war chest of hundreds of billions of dollars. A
consortium that has that kind of clout can freeze out other
competitive consortiums by its first mover advantage.

Think about it. You see what your competitor is up to when it joins
the consortium and you try to establish a rival consortium. Are you
really ready to risk all that money against a rival that is perhaps
now operational, has the best partners, and is locking up the
customers with long term supply contracts, has gotten the best lunar
sites, retreived the lowest delta-v NEOs, has locked up the best
talent. No, just as Ford, GM, and Chrysler had the market locked up
for years, so too will this consortium. At least until the amount of
capital in the world markets increases to a point where the orbital
economy makes room for new entrants just like the auto industry made
room for Toyota, Honda, Hyundai, Mitsubishi, Fiat, Yugo, Lada, etc.

I don't see much future for the small fry UNTIL there is an
established orbital economy. The small fry need the infrastructure
in order to operate. There is no money to be made in building and
operating the infrastructure until such time as there is an economy.

I'm aware of your interest in the MULE concept but I honestly don't
see it as a bootstrapping step. Rather it is another one-off
business venture that is tied to the Earth's economy. It may be
successful but it'll be isolated as a component of a potential
economy to be.

Think of it this way.

It makes makes little economic sense to spend billions developing a
MULE platform if no one wants to rent space in it.

So to directly answer your question, if you can act as the catalyst
to the formation of the the consortium, then I believe that things
can get rolling sooner.

I don't think it likely though, not as long as there are investment
opportunities on Earth that are lucrative. When there is more money
chasing fewer opportunites and driving returns down, that's when
you'll be seeing the massive move into orbit - because it's sheer
size will make it defensible.

After that, will come the entrepeneurs and the small fry. Further,
the serendipitous results of working in , creating for, and being
inspired by, an environment of cheap energy, cheap temperature
control, cheap vacuum and cheap access to variable gravity will
result in new technologies, new products, and new wealth.

>
> > No Mars mission, which will be a one-off mission with no legacy
> > hardware.
>
> Oh, yes. I could not agree with you more. I support going to Mars,
> but only in the context of a detailed plan for the SYSTEMATIC
> development of space.
>
> > Rather, lay down the roads, water pipes and electricity
> > grid and let those assets be the legacy for future users and
> > missions. Then will come the farmers, oil prospectors,
> > saloonkeepers, shopkeepers, doctors, dentists, settlers,
> > schoolmarms, etc.
> >
> > Any chance of this happening? Nope!
>
> Oh, no. Uuggh. I guess that answers some of my questions above.
> Drats! You really don't think there's any chance? No way to
motivate
> the private sector? I would think there could be lots of money to
> whomever or whatever develops that infrastructure.
>
> Jack

I'm curious on what basis you believe there would be lot's of money
to be made and how much infrastructure is needed before money can be
made, and who would pay to use that infrastructure?

I guess, where we differ is that I think the infrastructure is a
means towards a profit-generting end, and not a profit-generating
end in itself. That end must be a product which earns enough to
finance that infrastructure otherwise no investment will flow to
create the infrastructure.

TangoMan