Burt Rutans plans for a manned mission to Mars

wrote:

:On Fri, 12 May 2006 03:34:02 GMT, Fred J. McCall
wrote:
:
:If we can lift enough mass to put up a space elevator we don't need a
:space elevator.
:
:?? ROTFL!! "If we can send enough men and supplies and equipment and
:rails and crossties all the way across the continent to build a
:railroad, we don't need a railroad."

Cute, but hardly the same thing.

Calculate the mass of your space elevator. Now figure out what it
costs to put up at current launch costs.

If launch costs come down enough for a space elevator to be
economically practical, launch costs are so low that the elevator is
redundant.

It'd be used more for bringing stuff DOWN rather than bringing stuff
up at that point.

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

"Monte Davis" wrote in message
...
On Thu, 11 May 2006 10:07:17 -0400, "Jeff Findley"
wrote:

Hopefully lower launch will stimulate
demand which will provide for economies of scale which will lower launch
costs even more... You get the picture. Basic economics at work.

The operative word here is "hopefully." As there's no clear example of
cost/demand elasticity in 49 years of space activity, all hopes that
it will kick in Real Soon Now are based on dubious analogies to other
forms of transportation.

"Nice monoplane you got there, Lindy. Now... this pile here is the
building materials for Paris..."

Yet after a bit more development over the years, you get to the C-47 and the
Berlin Airlift.

This sort of thing will start gradually. Costs are still so high right now
that a little change in price doesn't result in much of a change in demand.
Bring down costs by an order of magnitude and demand ought to go up.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

Jeff Findley wrote:

Hopefully lower launch will stimulate
demand which will provide for economies of scale which will lower launch
costs even more... You get the picture. Basic economics at work.

The operative word here is "hopefully." As there's no clear example of
cost/demand elasticity in 49 years of space activity, all hopes that
it will kick in Real Soon Now are based on dubious analogies to other
forms of transportation.

"Nice monoplane you got there, Lindy. Now... this pile here is the
building materials for Paris..."

Yet after a bit more development over the years, you get to the C-47 and the
Berlin Airlift.

This sort of thing will start gradually. Costs are still so high right now
that a little change in price doesn't result in much of a change in demand.
Bring down costs by an order of magnitude and demand ought to go up.

But right now we are wasting money like it's going out of style. If we
give NASA even more money, they will waste it in even a more spectacular
fashion. If we are going to waste money on space, like we have wasted
money on homeland security after 911, or how we are wasting money every
month in Iraq, at a huge cost in human lives no less, then we need to
actually get something for our money wasted. VSE and ESAS are not it.

I posit that something for our money will have to be credible cryogenic,
liquid powered, single stage to orbit, space colonization ready launch.

Otherwise, we've got nothing.

http://cosmic.lifeform.org
http://www.lifeform.org/rocket.htm

wrote:
On Fri, 12 May 2006 03:34:02 GMT, Fred J. McCall
wrote:

"steve" wrote:

:There is one potentially cheap way of getting into orbit that is just
:about possible to achieve with current materials and that is the
:rotating space elevator. This requires a long cable approx 1000km
:length attached to either a large mass at one end in low Earth orbit or
:twice the length without the mass (double ended).
:This cable rotates at such a speed that even though at the Cg is at
rbital speed the lower end is travelling at a much slower speed
:allowing sub-orbital craft and even potentially aircraft to transfer
:mass which will then be transported upto orbital speed by the cable.
:Powering the whole cable, could be achieved by electro means or plasma
:drives.
:
:This will be built within the next decade I believe.

Yeah? How do you think they'll get it up?

It would most likely be constructed in space, from lunar or asteroidal
materials -- so a decade does seem rather optimistic.

However, sending it up by a bootstrap process is not as far-fetched as
you might imagine. The rotating elevator has one great, overwhelming
advantage over rockets: positive feedback. You can start with a very
small modular system that can't lift very much and requires the
payload to be boosted to near orbital speed before it hooks it; but if
the payload is more elevator modules, the system quickly becomes more
powerful, able to lift more payload and/or from a lower boost speed.

Because even the very small initial system's lifting capacity is
enormously larger than any contemplated rocket-based system -- it can
lift a payload several times a _day_ -- if it is initially devoted
entirely to strengthening itself, in a very short time it would be
able to lift a 10-ton payload from the back of a subsonic aircraft. A
short time after that, it would be able to lift a standard 40-foot
shipping container full of stuff right off the ground. More arms can
then be added to make a "pinwheel," tripling or quadrupling its
lifting capacity, to thousands of tons per day.

You're confusing an elevator with a rotovator.

An interesting point about rotovators is that they're not good for
reaching their orbit. They're very good at reaching higher orbits. In
fact, with a rotovator operating, Low Earth Orbit would be pretty much
abandoned.

"Jeff Findley" wrote:

"Monte Davis" wrote in message
.. .
On Thu, 11 May 2006 10:07:17 -0400, "Jeff Findley"
wrote:

Hopefully lower launch will stimulate
demand which will provide for economies of scale which will lower launch
costs even more... You get the picture. Basic economics at work.

The operative word here is "hopefully." As there's no clear example of
cost/demand elasticity in 49 years of space activity, all hopes that
it will kick in Real Soon Now are based on dubious analogies to other
forms of transportation.

"Nice monoplane you got there, Lindy. Now... this pile here is the
building materials for Paris..."

Yet after a bit more development over the years, you get to the C-47 and the
Berlin Airlift.

Which in the end depended on massive infrastructure already being in
place, in Berlin, in Europe, and here Stateside. The Airlift worked
because that infrastructure was already in place for other purposes.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

"Alex Terrell" wrote:

:Who mentioned a space elevator?
:
:Steve was talking about a rotovator, which could mass as little as 200
:tons, of which 3/4 is anchor mass.

Show your work. How many ounces are you lifting per cycle?

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

Fred J. McCall wrote:
"Alex Terrell" wrote:

:Who mentioned a space elevator?
:
:Steve was talking about a rotovator, which could mass as little as 200
:tons, of which 3/4 is anchor mass.

Show your work. How many ounces are you lifting per cycle?

Not my work - the formulae are exceedingly complex, but check slide 6
of this

http://www.niac.usra.edu/files/libra...9/355Bogar.pdf

or this for more detail:

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

Best to skip the bit about the plane.

With a material twice as strong a Spectra, system mass is 131 times
payload mass, of which 120 is anchor mass. The anchor mass would make a
good use for old rocket stages.

"Alex Terrell" wrote:

:
:Fred J. McCall wrote:
: "Alex Terrell" wrote:
:
: :Who mentioned a space elevator?
: :
: :Steve was talking about a rotovator, which could mass as little as 200
: :tons, of which 3/4 is anchor mass.
:
: Show your work. How many ounces are you lifting per cycle?
:
:Not my work - the formulae are exceedingly complex, but check slide 6
f this
:
:http://www.niac.usra.edu/files/libra...9/355Bogar.pdf
:
r this for more detail:
:
:http://www.tethers.com/papers/HASTOLAIAAPaper.pdf
:
:Best to skip the bit about the plane.
:
:With a material twice as strong a Spectra, system mass is 131 times
ayload mass, of which 120 is anchor mass. The anchor mass would make a
:good use for old rocket stages.

So all we need is a hypersonic cargo plane that we can't build, a
material with a tensile strength twice what we have, and a willingness
to transfer 1 ton cargoes during Mach 12 rendezvous at 300,000 feet.

Yeah, I see that happening in the next decade....

This is another one of those things. If we can build a hypersonic
transport with those capabilities, why not just push a little harder
and take it all the way to orbit? That has to be easier and cheaper
than all this other stuff (not to mention safer).

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

On Fri, 12 May 2006 14:00:36 GMT, Fred J. McCall
wrote:

wrote:

:On Fri, 12 May 2006 03:34:02 GMT, Fred J. McCall
wrote:
:
:If we can lift enough mass to put up a space elevator we don't need a
:space elevator.
:
:?? ROTFL!! "If we can send enough men and supplies and equipment and
:rails and crossties all the way across the continent to build a
:railroad, we don't need a railroad."

Cute, but hardly the same thing.

Calculate the mass of your space elevator. Now figure out what it
costs to put up at current launch costs.

Why? I have already described the bootstrap process that refutes that
arugment.

If launch costs come down enough for a space elevator to be
economically practical, launch costs are so low that the elevator is
redundant.

It's the elevator itself that brings them down, by building itself. I
have already informed you of that. Can't you read?

-- Roy L

On 12 May 2006 12:28:53 -0700, "Alex Terrell"
wrote:

You're confusing an elevator with a rotovator.

Where I come from, farmers use rotovators.

An interesting point about rotovators is that they're not good for
reaching their orbit. They're very good at reaching higher orbits.

Reaching their own orbit takes a little doing, but is possible.

-- Roy L