"Rockets not carrying fuel" and the space tower.
Robert Clark
provided by a highly pressurized fluid piped up from the ground [you
may need to use a fixed-width font such as Courier New to properly view
the diagram.]
A key aspect of the proposal as desccribed below is that the material
forming the pipeline does not have to be especially strong as for
example to support its own weight. The force for supporting each
portion of the pipeline is provided by the thrust produced by
pressurized fluid vented along the entire length of the pipeline.
Note that this also would provide a means of producing a space tower
or space elevator (to low Earth orbit). You really wouldn't need to
attach a rocket to the end of the rocket itself. You would use the
pipeline to *slowly* raise the payload to the required altitude for
LEO. Then you could use a rocket attached to the payload only to give
the payload the required tangential orbital velocity. Note that the
fuel and rocket that would need to be attached to the payload would be
significantly less since this fuel would not be used for getting it up
to altitude.
You could have this "space fountain" raised only when you wanted to
launch a payload, or you could have it permanently raised in the air.
This would work if you located the fountain next to a large permanently
flowing source of water such as a river. Then for example a ram pump,
which requires no moving parts, could be used to raise the water in the
fountain:
Contents for the pulser pump section of Gaiatech.
http://members.tripod.com/~nxt wave/gaiatech/pulser/index.htm
Designing a Hydraulic Ram Pump.
http://www.lifewater.org/resources/rws4/rws4d5.htm
Bob Clark
**********************************************************************************
Newsgroups: sci.astro, sci.physics, sci.mech.fluids, sci.engr.mech,
sci.space.policy
From: rgregorycl...@yahoo.com (Robert Clark)
Date: 20 Nov 2004 17:04:01 -0800
Local: Sat, Nov 20 2004 5:04 pm
Subject: Re: "Rockets not carrying fuel" for orbital transfer.
"George Dishman" <george.dish...@clara.co.uk> wrote in message
<news:11005508...@damia.uk.clara.net>...
> "Robert Clark" <rgregorycl...@yahoo.com> wrote in message
> news:832ea96d.04111...@posting.google.com...
> >...
> > I came up with two other ideas for reducing the weight of the fluid
> > that had to be supported by the rocket as the tube trails behind
the
> > rocket.
> > Firstly, I wanted to investigate both the possibilities of using
> > gaseous hydrogen or liquid hydrogen for the fluid carried by the
tube.
> That drops the density so you need much higher
> speeds for the same flow rate so makes everything
> more difficult.
> > However, the liquid hydrogen scenario just gave too much weight.
But
> > suppose the rocket didn't have to provide the propulsion for the
fluid
> > in the tube? This is what I envision:
> <Snip pictures>
> All you have done is use a compound engine. The
> same mass is being accelerated to the same speed
> so will need the same fuel. You are forgetting
> the engines not only lift the craft but also the
> fuel needed to lift themselves. In fact with more
> engines, you have greatly increased the mass and
> the fuel needed, and all these schemes create a
> huge drag with air friction on the tube which also
> needs more fuel.
> Instead, imagine using a nearly rigid pipe as the
> arm of a trebuchet to pump fuel only over the first
> few seconds. That might be practical though the
> risks during disconnection are significant.
> George
I'm also investigating the possibility of using a rigid structure to
reach into LEO. However, I think the efficiency of the tube method is
better than you suggest.
Let's go back to the case of launch from Earth to LEO. I'm still
considering here that you're not using engines to combust fuel but are
only conducting a high pressure fluid up the tube to provide
propulsion. So the weight of the exhaust ports is quite small, not
that of a full blown engine.
Let's estimate the the size of these exhaust ports.
^
|
|
Towards the rocket.
| |
| |<----Fluid carrying tube.
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\
// | | \\
| |
| |
| |
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\<---Exhaust ports directed aft.
// | | \\
| |
| |
| |
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\
// | | \\
| |
| |
| |
Let's say you put a pair of these ports every 100 meters. Then each
pair of ports would only have to provide the thrust to support the
weight of 100 meters of the tube and fluid. Let's use liquid hydrogen
now. Its density is 71 kg/m^3. The volume of a 100 m tube, .3m wide is
Pi*(.15)^2*100 = 7.07 m^3. So the mass is 71 kg/m^3 times this or
about 502 kg, 1104 lbs.
We're still using the presumption that we can communicate, say, a
pressure like the 6400 psi pressure produced by the shuttle liquid
hydrogen turbopumps up the tube. (Whatever type of pumps we use would
be located on the ground not the rocket so can be quite large.) Now we
want two exhaust ports to support 1104 lbs., or 552 lbs. each. So 552
lbs = (pressure)*(square area of ports) = 6400 * Pi * (1/4)*(diameter
of ports)^2 . We get a diameter of .33 in or 8 millimeters. Actually
they might even be smaller than this by using convergent-divergent
type nozzles used with rockets.
Now remember the entire tubes weight is supported by these exhaust
ports so the great majority of the fluid that reaches the rocket will
be driving only the payload and rocket. For a .3m = 12in wide tube
this could be a thrust of 6400 * Pi * 6^2 = 723,824 lbs. that is
solely used to loft the payload and (engineless) rocket, and again we
can probably do better than this using the nozzles normally used on
rockets.
Note that we can get even more thrust from the exhaust ports by
making them wider or by using more than 2 at each level. This is
important since we can also solve the hypersonic drag problem. These
exhaust ports are not engines but it would be a simple (and light
weight matter) to give them directional ability. Then you could have
them automatically direct their thrust to counteract the drag caused
by each portion of the tube.
Bob Clark
**********************************************************************************
Uncle Al
>
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground [you
> may need to use a fixed-width font such as Courier New to properly view
> the diagram.]
> A key aspect of the proposal as desccribed below is that the material
> forming the pipeline does not have to be especially strong as for
> example to support its own weight. The force for supporting each
> portion of the pipeline is provided by the thrust produced by
> pressurized fluid vented along the entire length of the pipeline.
What percentage of the inflow makes it to the top, git? What is the
weight of a 50-mile depth of liquid oxygen, git?
> Bob Clark
so sad.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
Don A. Gilmore
news:42487FF4...@hate.spam.net...
> Robert Clark wrote:
> >
> > I copied below a proposal for space access where the propulsion is
> > provided by a highly pressurized fluid piped up from the ground [you
> > may need to use a fixed-width font such as Courier New to properly view
> > the diagram.]
> > A key aspect of the proposal as desccribed below is that the material
> > forming the pipeline does not have to be especially strong as for
> > example to support its own weight. The force for supporting each
> > portion of the pipeline is provided by the thrust produced by
> > pressurized fluid vented along the entire length of the pipeline.
> [snip]
>
> What percentage of the inflow makes it to the top, git? What is the
> weight of a 50-mile depth of liquid oxygen, git?
Not to mention pressure.
Don
Kansas City
redneckj
"Don A. Gilmore" <eromlig...@kc.rr.com> wrote in message
news:3are8cF...@individual.net...
> Don
> Kansas City
>
>
Uncle Al
I did - that is the weight of the column/area. Gonna cost ya dear in
mgh, PV, cone fittings, and foot-thick walled piping at the bottom.
Cryogenic metal loses strength. Vacuum insulation does poorly in
(1 cm)(1 cm)(50 miles)(5280 feet/mile)(12 in/ft)(2.54 cm/in)(1.14
g/cm^3)(0.0022046 pounds/gram)(6.4516 cm^2/in^2) = 130,473 psi plus
static compression of the liquid.
high pressure environments. And you have to fill the pipe before
anything in becomes something out. Not only is it a stooopid idea, it
is a stooopid Fermi idea.
Mike Rhino
laser. In that case, the rocket would still need fuel, but it wouldn't need
anything that burns. The fuel tank would contain ammonia and nothing else.
The back of the rocket would have a concave mirror that concentrates the
laser light on one spot. Ammonia would be sent to that spot, heat up, and
be ejected as exhaust.
mme...@cars3.uchicago.edu
than saying "I'm high tech, I'm using a laser":-)
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
bz
news:NC12e.19$45....@news.uchicago.edu:
> In article <ky12e.60128$xX3....@twister.socal.rr.com>, "Mike Rhino"
> <octob...@alexanderpics.com> writes:
>>If you wanted to send energy to a rocket, you would be better off with a
>>laser. In that case, the rocket would still need fuel, but it wouldn't
>>need anything that burns. The fuel tank would contain ammonia and
>>nothing else. The back of the rocket would have a concave mirror that
>>concentrates the laser light on one spot. Ammonia would be sent to that
>>spot, heat up, and be ejected as exhaust.
>>
> And the advantage over "something that burns" would be? I mean other
> than saying "I'm high tech, I'm using a laser":-)
>
The energy to orbit a vehicle can be generated on earth and beamed to the
vehicle, rather than trying to carry all that energy(mass) with you.
You don't even need to carry fuel. Heated Air can act as a pulse jet.
If you want to carry a reaction mass, why not water?
http://www.space.com/businesstechnology/technology/laser_propulsion_
000705.html
Google for
"laser powered" spacecraft launch
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
Mike
"Robert Clark" <rgrego...@yahoo.com> wrote in message
news:1112043120....@f14g2000cwb.googlegroups.com...
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground
>Bob Clark
>
Hello,
It seems you are presenting a proposal that appears in essence an attempt at
solving some of the dilemmas associated with the desire to achieve safe and
efficient interstellar space travel.
Have you considered the ethical dilemmas of such a proposal?
Projecting our malignant, unrefined, chaotic microcosm into something on a
galactic scale would create a condition of unfathomable horror.
For instance, say you are now allowed to go zipping around the galaxy like
something akin to star trek. The first reason of necessity why one would
find the need to branch out according to the conditions of our present
malignancy would be economic. Simply put, for our condition to strengthen
and prosper we need to find more raw materials to convert into goods and
services; this means raw materials and resources of all kinds including new
living space.
So let's say after several months of searching you find a planet with
resources available for conversion and consumption. The only ethical dilemma
is, there happens to be some life forms inhabiting your newfound planet that
are at some intermediate stage along their higher evolutionary process.
Would you find it ethical to brush these indigenous life forms aside and
start tapping the planet for resources? By doing so you would be aborting
the planets higher evolutionary processes. Think if that planet was this
planet in prehistoric times invaded and consumed along with the evolutionary
progress of the entire human race.
Rather than searching for that "needle in a haystack" in this galaxy by
attempting to increase the "velocity side" of the equation. One needs to
look at the possibility of reducing the "travel time" side of the equation.
What will better cure this planet are not more cheep resources but that
instead a massive dose of synergy.
Kirk Gordon
> "Robert Clark" <rgrego...@yahoo.com> wrote in message
> news:1112043120....@f14g2000cwb.googlegroups.com...
>
>
>>I copied below a proposal for space access where the propulsion is
>>provided by a highly pressurized fluid piped up from the ground
>
Good grief!
He's not doing any interstellar travel, Mike. In fact, if the
hydrogen pipe thingy is the best he can come up with, he won't even get
above the treetops. The big problem with spreading humans around the
galaxy isn't that we'll do terrible harm; but that we'll embarrass
ourselves when other sapient critters find out how goofy we can be.
And the main, long-term, fundamental reason for going into space
isn't to get rich. It's to stay alive. As Heinlein said: The
dinosaours are extinct because they didn't have a space program. And we
don't have one either, in any sense that'll serve our survival needs
when ANOTHER major asteroid or comet decides to pay a visit.
WE'RE the lifeforms who are likely to be "swept aside" if we're
foolish enough to think that we can live forever on one fragile little rock.
KG
Matt
on a
galactic scale would create a condition of unfathomable horror."
Well Mike, I guess the only thing you can do is to act for good in your
own life; take the first step for a better universe, and GO CHOKE
YOURSELF! We've hardly made it off the planet! We probably won't have
boots on the ground anywhere outside the solar system for hundreds of
years!
As for fuelless rockets, why didn't the mass driver ever go anywhere.
Granted anything you launch in it has to be able to withstand seriously
extreme acceleration, but we could keep some rockets for the sensitive
stuff and launch all the bulk into orbit with the mass driver. I
wouldn't even think it would be terribly expensive to build compared to
say your average space "total waste of money, should've been retired
years ago" shuttle launch.
Matt
a bit further away to avoid any nearby nova, supernova, x-ray burst,
etc. or even an especially bad solar flare from our own sun.
Mike
this solar system and no further, I guess it would be ok.
I doubt there would be few if any ethical issues.
Mike
I was talking about ethics you dumb fuck!
"Matt" <mam...@gmail.com> wrote in message
news:1112078175....@z14g2000cwz.googlegroups.com...
Morituri-|-Max
"Mike" <M....@verizon.net> wrote in message
news:rI72e.33814$mq2.12588@trnddc08...
> Oh...well then, if Mr. Clark was only wanting to explore the planets
> within
> this solar system and no further, I guess it would be ok.
> I doubt there would be few if any ethical issues.
Whew.. good thing we have your permission.. man, for a second there I
thought our future was in jeaporady.
What is ethical about ensuring mankind becomes extinct because you decide we
can't leave our planet? If there are so many beings out there we could
harm, why haven't they gotten together with us yet to work out a good plan
for how we will spread into the galaxy when we finally can?
Morituri-|-Max
> Non sequitur and flame off.
> I was talking about ethics you dumb fuck!
Hmmm, after reviewing his post below, I find it strange that someone talking
about ethics (you) resorts to the f-word right off the bat, when the poster
below didn't use any vulgar words to attack you. Is this how all your
"debates" go?
Don A. Gilmore
news:Ij82e.55397$8D....@tornado.texas.rr.com...
You kids have been watching way too much TV.
Don
Kansas City
Uncle Al
Stupid idea. Energy interception scales as the square of dimension,
rocket mass scales as the cube. Only good for corrupt demos.
Morituri-|-Max
> You kids have been watching way too much TV.
I was being sarcastic. 8 )
Henry Spencer
<mme...@cars3.uchicago.edu> wrote:
>>If you wanted to send energy to a rocket, you would be better off with a
>>The back of the rocket would have a concave mirror that concentrates the
>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>be ejected as exhaust.
>
>And the advantage over "something that burns" would be? I mean other
>than saying "I'm high tech, I'm using a laser":-)
1. You can raise the exhaust gas to higher temperatures -- giving more
energy to be converted into exhaust kinetic energy -- if you aren't
limited by the energy content of chemical fuels.
2. You can choose exhaust gases with better gas properties -- which
convert heat more efficiently into kinetic energy -- if the gases don't
have to be combustion products. Ammonia in particular, when you get it
hot, breaks down into nitrogen and a lot of hydrogen, giving really
excellent gas properties.
Depending on design approach, the flying hardware may also be simpler.
(The laser is complicated, but it's on the ground, where mass doesn't
matter and maintenance is easy.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert | he...@spsystems.net
Henry Spencer
bz <bz...@ch100-5.chem.lsu.edu> wrote:
>You don't even need to carry fuel. Heated Air can act as a pulse jet.
Only briefly. Practical vehicles want to do most of their accelerating
up above the atmosphere, where there's no drag or aerodynamic heating.
Whether it's worth trying to exploit air on the way up is debatable, but
certainly much of the accelerating has to be done as a rocket, if you
want manageable engineering.
>If you want to carry a reaction mass, why not water?
Water is stubbornly stable, and when you do get it hot enough to break
down into hydrogen and oxygen, it soaks up a lot of energy doing so, and
keeps trying to recombine. Ammonia breaks down much more easily, and
stays broken down.
Henry Spencer
Matt <mam...@gmail.com> wrote:
>As for fuelless rockets, why didn't the mass driver ever go anywhere.
>Granted anything you launch in it has to be able to withstand seriously
>extreme acceleration, but we could keep some rockets for the sensitive
The idea isn't ridiculous, but it's tricky to make it work well on Earth's
surface, where payloads have to punch out through the atmosphere. The
engineering is challenging, and building one would be a big expensive
project. And there is basically no money for developing new unorthodox
launch systems; there is little money even for new orthodox ones.
>wouldn't even think it would be terribly expensive to build compared to
>say your average space "total waste of money, should've been retired
>years ago" shuttle launch.
Remember, the cost of the shuttle is almost all "standing army" -- it's
mostly the cost of maintaining the facilities and operations teams. You
don't save anything much by canceling one launch. (The shuttle budget has
been higher than ever for the last two years, with the launch rate zero
because the shuttle is grounded.) To see major savings, you have to close
down the whole program, and preferably mothball the VAB and LC-39.
Henry Spencer
Uncle Al <Uncl...@hate.spam.net> wrote:
>> If you wanted to send energy to a rocket, you would be better off with a
>> laser. In that case, the rocket would still need fuel, but it wouldn't need
>
>Stupid idea. Energy interception scales as the square of dimension,
>rocket mass scales as the cube.
So? This just means that laser launchers work better with small vehicles.
But that's true anyway. The dominant cost is the cost of the laser, and
that is pretty much directly proportional to vehicle size -- you need very
roughly a megawatt of laser per kilogram of payload -- and almost totally
independent of launch rate. So laser launchers, like guns, catapults,
etc., want to launch lots of little payloads rather than a few big ones,
holding the capital investment down and keeping the expensive hardware
busy. They're conveyor belts rather than pickup trucks.
Alain Fournier
Henry Spencer wrote:
> In article <NC12e.19$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser. ... The fuel tank would contain ammonia and nothing else.
>>>The back of the rocket would have a concave mirror that concentrates the
>>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>>be ejected as exhaust.
>>
>>And the advantage over "something that burns" would be? I mean other
>>than saying "I'm high tech, I'm using a laser":-)
>
>
> 1. You can raise the exhaust gas to higher temperatures -- giving more
> energy to be converted into exhaust kinetic energy -- if you aren't
> limited by the energy content of chemical fuels.
Avoiding engine meltdown is already a problem with chemical fuel
rockets. Does this mean that laser rockets would have to have
either exhaust temperatures similar to chemical rockets, or
have very low thrust à la ion engine rockets?
Alain Fournier
vonroach
wrote:
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser.
No, a well designed solar panel.
mme...@cars3.uchicago.edu
>In article <NC12e.19$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser. ... The fuel tank would contain ammonia and nothing else.
>>>The back of the rocket would have a concave mirror that concentrates the
>>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>>be ejected as exhaust.
>>
>>And the advantage over "something that burns" would be? I mean other
>>than saying "I'm high tech, I'm using a laser":-)
>
>1. You can raise the exhaust gas to higher temperatures -- giving more
>energy to be converted into exhaust kinetic energy -- if you aren't
>limited by the energy content of chemical fuels.
You can raise the exhaust gas to higher temperature if you can deliver
more energy than this present in fuel carried on board. I posted
elsewhere the numbers required. As of now, you're short by many
orders of magnitude.
>
>2. You can choose exhaust gases with better gas properties -- which
>convert heat more efficiently into kinetic energy -- if the gases don't
>have to be combustion products. Ammonia in particular, when you get it
>hot, breaks down into nitrogen and a lot of hydrogen, giving really
>excellent gas properties.
>
>Depending on design approach, the flying hardware may also be simpler.
>(The laser is complicated, but it's on the ground, where mass doesn't
>matter and maintenance is easy.)
This is all lovely, once you've operational multi GW lasers, and the
means to power them, and the means to dissipate the waste heat
generated. Way to go.
Mike Rhino
> Ditto, but while Mars would save us from an asteroid, we'll have to be
> a bit further away to avoid any nearby nova, supernova, x-ray burst,
> etc. or even an especially bad solar flare from our own sun.
Would hiding inside an asteroid protect you from those?
Diginomics
> can't leave our planet?
Precisely. It is illogical from the historical point of view to enter
into the atomic age with the belief that the speed of light is a true
law, if you wish to be around for long as a living planet. The
argument must then hinge on whether because of wartime secrecy, did we
enter the atomic age off-balance? Is not the counter-balance to the
MAD doctrine, this contrived and deliberately slanted "theoretical
relativity" against all that is interstellar? After-all in the MAD
political climate, a way-out to the stars would undermine such a
doctrine if one side's leaders could take refuge in the stars while
each side fought it out to the end. Also the MAD doctrine required all
atomic materials to be dedicated to the production of deterrent, and
not reserved for space propulsion experiments. The NASA comment on
Dyson's history of Project Orion even acknowledges such uses would now
be quite convenient for using up the now no longer required atomic
assemblies. Even more I would say, for if reaching the stars were a
rampant success, the H assemblies would be dismantled to release the A
assemblies as much needed propulsion propellants. Then we could get to
the sensible stage in atomics where the very assembly of an H would be
an act of war-like aggression. Still wouldn't stop an errant space
pilot captain dropping a propulsion pellet on top of an unfriendly
city, but mankind would have progressed beyond the very dangerous
"all-or-nothing" mentality towards world peace we still are locked
into. Orion of course needs revised. Ground launches are unacceptable
and belong to the project period when standard chemical based payload
launches were in their infancy. Pusher-plates even if they were not a
technical fantasy, are also unacceptable outside of the project period
where billion dollar satellite systems were non-existent and hence not
a prohibitive cost to absorb in collateral damages. America perhaps
need to have a long look at what happened to the Chinese empire
hundreds of years ago when it failed to champion containment of
gunpowder. Coca-cola need not really provide technical insight for
such project innovations, when 1,100 years of human history have been
about containing explosions within a hollow cylinder closed at one end
with a pusher-plate. Known by the "non-techs" as the cannon or firing
tube! It does not need re-inventing this wheel! No sir! As for
relativity. If we had had the luck to enter the atomic age in a period
of peace with less fear and secrecy, perhaps relativity would have a
different more positive slant. If you wish to slant F=MA to advocate
interstellar travel, think to make "Acceleration" relative to
planetary gravities. That is to say it is not good enough to say there
is no light speed barrier (or that the barrier is found at C squared
or C to the power of another C). Rather that "relatively" acceleration
diminishes as an effect on the human body at C+ speeds when outside
the real "pull acceleration" of natural planetary gravities. Our
observation that 1 G acceleration in a rocket leaving earth is felt as
2G on the body, should not be automatically assumed to be the same as
2G acceleration in a gravity-less space environment. String theory
might help, but basically slanting relativity away from the concerns
of MAD is to say artificial accelerations are relative to planetary.
Anyone care to come up with a top G "lovingly endured" reaching a 20
light year distant planet, travelling at a maxium speed of 10C. That
is to say accelerating at a constant until reaching a peak speed
half-way of 10C and then de-accelerating the remainder to arrive
static.
If you wish for a further look at my proposed Orion revision, seek out
the ACCTOPE design on www.tide2000.com/feedback
"Morituri-|-Max" <new...@sendarico.net> wrote in message news:<Ij82e.55397$8D....@tornado.texas.rr.com>...
Matt
You were discussing ethics in a physics forum, which would be quite
understandable if the ethics you were discussing will have something to
do with decisions being made by scientists in the next hundred years or
so. If you believe this is the case with respect to your point then I
would dare say you're not very bright. If you didn't believe that your
point was relevant, then you should expect ridicule when you knowingly
post in an inappropriate forum.
If the point you were making is that we should abandon scientific
funding of space research in favor of increased funding on social
spending, or generic international cooperation, then I would say that I
disagree with you (and this should be discussed in a political forum).
If you are an agitator, as I assumed, then I do not apologize for
insulting you.
If you are just not very bright, then I'm very sorry and I wish you all
the best in your studies.
dlzc1 D:cox T:net@nospam.com N:dlzc D:aol T:com (dlzc)
"Mike Rhino" <octob...@alexanderpics.com> wrote in message
news:cap2e.694$e06...@twister.socal.rr.com...
Who wants to live as a mole? How many generations will you hide?
David A. Smith
Earl Colby Pottinger
No, depending on the design a laser heated engine can have temperature well
above that of chemical rockets because there is no combustion.
In a chemical rocket the entire volume of the combustion chamber is pretty
much all the same temperature - hot combustion gasses touch the walls of the
rocket engine and cooling the walls like you say can be a problem if there is
any mistakes in the design.
In a laser heated rocket the flux of the laser while high can be still low
enough to handle and then is focused to heat the gasses away from the
material walls of the rocket. The relative cooler gasses near the walls can
still be within material/design limits.
Another possible design would be to heat the entire rocket engine but use as
your reaction gas a very light weight fuel (example hydrogen, helium
ammonia). Normally you would need to burn an oxidzer with a fuel resulting
with a heavier molecular weight in your exhaust at a given temperature -
ofcourse you can burn helium.
So let's say as an example 3000 degree K is a hard limit in hot we can run a
rocket engine.
From the kinetic energy formula we find: v_{rms}^2 = 24,940 T / molecular
mass with v in m/s and T in kelvins.
For standard temperature 0C or 273K the root mean square speeds are:
* hydrogen 1846 m/s
* nitrogen 493 m/s
* oxygen 461 m/s
At 3000K I get
* hydrogen 6116 m/s which is a good exhaust speed above that of most
chemical rocket designs.
Earl colby Pottinger
PS. I thought STP was at 25C but www.answers.com uses 0C as STP.
--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp
Henry Spencer
<mme...@cars3.uchicago.edu> wrote:
>You can raise the exhaust gas to higher temperature if you can deliver
>more energy than this present in fuel carried on board. I posted
>elsewhere the numbers required. As of now, you're short by many
>orders of magnitude.
A more precise reference than "elsewhere" would be of interest, since
this doesn't agree with the numbers I've seen.
>>Depending on design approach, the flying hardware may also be simpler.
>>(The laser is complicated, but it's on the ground, where mass doesn't
>>matter and maintenance is easy.)
>
>This is all lovely, once you've operational multi GW lasers...
There is no requirement for them. You are, to borrow one of Bob Zubrin's
better phrases, "fantasizing about interplanetary battle cruisers". The
requirement is roughly a megawatt per kilogram of payload. You can get a
stream of payloads of practical size with 50-100MW, which would be costly
but shouldn't pose major development challenges.
A laser-launcher system which can carry *people* probably does need
GW-range lasers. But people, and other payloads which can't be subdivided
into small pieces, are a very small fraction of what we need to launch.
Henry Spencer
Alain Fournier <alai...@sympatico.ca> wrote:
>> 1. You can raise the exhaust gas to higher temperatures -- giving more
>> energy to be converted into exhaust kinetic energy -- if you aren't
>> limited by the energy content of chemical fuels.
>
>Avoiding engine meltdown is already a problem with chemical fuel
>rockets. Does this mean that laser rockets would have to have
>either exhaust temperatures similar to chemical rockets, or
>have very low thrust à la ion engine rockets?
Or designs quite different from those of chemical rockets. In one quite
appealing concept (alas, making it work well is challenging), the propellant
is just a slab of some convenient plastic. A small laser pulse vaporizes
a surface layer, and a much larger laser pulse following hot on the small
one's heels superheats the sheet of vapor. Because the expanding vapor
starts as a thin sheet on the solid surface, it inherently expands at
right angles to the surface, and no nozzle is required. Repeat briskly.
Setting aside that sort of innovation, more conventional near-term laser
rockets would probably rely mostly on better gas properties, and would not
try to get the gas a *lot* hotter. So they could be fuel-cooled in much
the same way as chemical rockets; ammonia and liquid hydrogen -- the two
obvious choices of propellant -- are both excellent coolants.
mme...@cars3.uchicago.edu
>In article <ZUk2e.7556$w63.6...@news20.bellglobal.com>,
>Alain Fournier <alai...@sympatico.ca> wrote:
>>> 1. You can raise the exhaust gas to higher temperatures -- giving more
>>> energy to be converted into exhaust kinetic energy -- if you aren't
>>> limited by the energy content of chemical fuels.
>>
>>Avoiding engine meltdown is already a problem with chemical fuel
>>rockets. Does this mean that laser rockets would have to have
>>either exhaust temperatures similar to chemical rockets, or
>>have very low thrust à la ion engine rockets?
>
>Or designs quite different from those of chemical rockets. In one quite
>appealing concept (alas, making it work well is challenging), the propellant
>is just a slab of some convenient plastic. A small laser pulse vaporizes
>a surface layer, and a much larger laser pulse following hot on the small
>one's heels superheats the sheet of vapor. Because the expanding vapor
>starts as a thin sheet on the solid surface, it inherently expands at
>right angles to the surface, and no nozzle is required. Repeat briskly.
>
direction but to cool them, as well. Basically, when you look at the
hot cloud of gas propagating down the combustion chamber, its energy
is a sum, E = E_cm + E_th, where E_cm is the energy of the center of
mass motion and E_th is the thermal energy. The first of the two
contributes to the thrust, the second doesn't. The purpose of a good
nozzle is transfer as much energy as possible from E_th + E_cm (thus,
effectively, cooling the exhaust). Without this big part of the
theoretically achievable thrust is wasted.
mme...@cars3.uchicago.edu
>In article <xUm2e.40$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>>You can raise the exhaust gas to higher temperature if you can deliver
>>more energy than this present in fuel carried on board. I posted
>>elsewhere the numbers required. As of now, you're short by many
>>orders of magnitude.
>
>A more precise reference than "elsewhere" would be of interest, since
>this doesn't agree with the numbers I've seen.
Did you try to calculate numbers, not just "see" them?
>
>>>Depending on design approach, the flying hardware may also be simpler.
>>>(The laser is complicated, but it's on the ground, where mass doesn't
>>>matter and maintenance is easy.)
>>
>>This is all lovely, once you've operational multi GW lasers...
>
>There is no requirement for them. You are, to borrow one of Bob Zubrin's
>better phrases, "fantasizing about interplanetary battle cruisers".
No, just one of the smaller rockets used to launch satellites
nowadays. Check out the power output of these rocket engines.
> The requirement is roughly a megawatt per kilogram of payload.
Quite optimistic:-)
> You can get a
>stream of payloads of practical size with 50-100MW, which would be costly
>but shouldn't pose major development challenges.
>
Unless you plan for maneuvering and assembly in orbit, most payloads
are quite larger than this.
bz
news:oKGdnWBjp4n...@look.ca:
> For standard temperature 0C or 273K the root mean square speeds are:
> * hydrogen 1846 m/s
> * nitrogen 493 m/s
> * oxygen 461 m/s
>
> At 3000K I get
> * hydrogen 6116 m/s which is a good exhaust speed above that of most
> chemical rocket designs.
Nitrogen might be a good 'non poluting' reaction mass.
>
> Earl colby Pottinger
>
> PS. I thought STP was at 25C but www.answers.com uses 0C as STP.
Different groups use different STPs.
>
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
jmfb...@aol.com
Have you ever tried to hit the broad side of a moving barn?
With your implementation what happens when you miss?
/BAH
Subtract a hundred and four for e-mail.
Earl Colby Pottinger
> This is all lovely, once you've operational multi GW lasers,
Yes, that is a problem.
> and the means to power them,
??? There are this things called power plants, and they do put out power in
the gigawatt range already. Ofcourse there are other energy storage system
like batteries and capicitors with a nice external power source called the
national grid. I don't see the problem if you have the type of money already
needed to build the lasers.
> and the means to dissipate the waste heat generated.
There are these things called bodies of water. If you don't have one they
are easy to make, getting rid of the heat is standard engineering too.
To me the only valid objection were the lasers. You just can't order ones
that large right now. But there is nothing to say that they can't be made if
enough research money is spent first.
Earl Colby Pottinger
Quantum Mirror
resources available for conversion and consumption. The only ethical
dilemma
is, there happens to be some life forms inhabiting your newfound planet
that
are at some intermediate stage along their higher evolutionary process]
You live in a fantasy world. The ability to travel space is a problem
of immense proportion. It will be 50 to 100 years to even reach mars.
That is in our own back yard. The nearest star is a problem that will
never be achieved in these fragile bodies. We will need to become
mechanical for that trip to ever take place! We are talking centuries
before such an attempt will even be made. I am sure our malignant,
unrefined, chaotic microcosm will have evolved by then.
Mike
"Quantum Mirror" <jun...@pgrb.com> wrote in message
news:1112204010.5...@g14g2000cwa.googlegroups.com...
>
> You live in a fantasy world. The ability to travel space is a problem
> of immense proportion. It will be 50 to 100 years to even reach mars.
> That is in our own back yard. The nearest star is a problem that will
> never be achieved in these fragile bodies. We will need to become
> mechanical for that trip to ever take place! We are talking centuries
> before such an attempt will even be made. I am sure our malignant,
> unrefined, chaotic microcosm will have evolved by then.
I agree with you, and so does everyone else that the ability to travel in
space is a problem of immense proportion. Let alone the desire for
interstellar space travel. Many people including myself have important ideas
and proposals on improving the situation.
Some of these proposals involve huge expenditures and engineering
breakthroughs.
See August 2003 edition of Discovery magazine. Robert Frisbee is the chief
engineer who directs the advanced propulsion concept studies at JPL.
Still all is not lost! There are alternatives to this dilemma. Let's take a
look at the amoeba.
Now this one celled organism has no brain to speak of; it can't think, it
has no dexterity, and no accumulated technology. Though when it finds itself
in a hopeless situation such as a slightly too acidic or alkaline
environment what does it do? It migrates! It attempts to move itself to more
suitable environment.
Rather than attempting to increase the velocity of the spaceship. There
might be a better result by changing the environment the spaceship is
travelling in. Hence the concept of "planetary migration"
I am not an anarchist; this plan does not violate Einstein's laws.
Theoretically a spaceship travelling at 7 miles per second can appear to be
travelling many more times the speed of light. If the spaceship is
travelling in an environment where travel time has been compressed. Those
conditions do not exist in this universe. Therefore it becomes necessary to
migrate.
Is anyone else on the same page as me with this concept? Perhaps a very
bright (but unknown) cosmologist located
in some obscure part of England? Or Australia? Ireland or Italy? Germany?
Japan?...... Canada?
bz
> Have you ever tried to hit the broad side of a moving barn?
> With your implementation what happens when you miss?
>
when you are at the train station and you are shooting at the back of a
departing train it makes it a bit easier to hit.
It is NOT like trying to intercept an incoming missle to knock it out with a
laser.
And 'if you miss' the thrust drops until you get back on target.
You keep adjusting your active adaptive focus mirror array and tracking the
rocket, so misses are not as likely as a poorly focused pulse.
Mike
"Morituri-|-Max" <new...@sendarico.net> wrote in message
news:Ij82e.55397$8D....@tornado.texas.rr.com...
>
> harm, why haven't they gotten together with us yet to work out a good plan
> for how we will spread into the galaxy when we finally can?
.Probably because they're having the same difficulties we're having getting
from point A to point B
an excessive ammount of travel time is required.
Russell Wallace
> Stupid idea. Energy interception scales as the square of dimension,
> rocket mass scales as the cube. Only good for corrupt demos.
I'd have thought the cube-square law applied to all engines? Don't the
flow rate of rocket engines, the strength of their mountings etc all
scale as the square of dimensions, or am I missing something?
(Not that I can see the point of paying for gigawatts of lasers just to
use ammonia instead of kerosene+lox combustion products as reaction
mass, nor a market for 50-kg payloads, but I wouldn't have thought
energy interception was a problem.)
--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.
Robert Clark
are doable with currently available tech.
You could for example use shuttle or Saturn V type engines on the
ground and direct the exhaust through the tubes upwards. These engines
have exhaust velocities in the range of 4000m/s. A particle sent upward
at this initial speed (ignoring atmosphere) could reach 800 km. At 100
km it would have a speed above 3700m/s, though the tube of course
induces frictional effects which will reduce this speed somewhat. To
resist the high temperatures you could coat the inside of the tube with
high temperature alloys such as:
tantalum hafnium carbide.
"The alloy tantalum hafnium carbide (Ta4HfC5), with a melting point of
4,215 C (7,619 F), is one of the most refractory substances known."
http://www.britannica.com/nobel/micro/254_6.html
You could instead have plasma engines provide the high velocity fluid
on the ground. Plasma engines can have exhaust velocities at hundreds
of thousands of meters per second:
Plasma Rockets
"High exhaust velocity can be achieved by the use of a plasma, where
the atoms of the gas have been stripped of some of their electrons,
making it a soup of charged particles. The temperature of a plasma
starts at about 11,000° C. But present day laboratory plasmas can be a
thousand times hotter. Particles in such plasmas move at velocities of
300,000 m/sec. These temperatures are comparable to those in the
interior of our Sun. No known material could survive direct contact
with such a plasma. Fortunately, a plasma responds well to the presence
of electric and magnetic fields. A magnetic channel can be constructed
to both heat and guide a plasma, without ever touching material walls."
http://t2spflnasa.r3h.net/shuttle/support/researching/aspl/propulsion.html
Since the plasma is sent through a tube you could have the electrical
power sent up with the tube to create the E/M fields required to keep
the plasma away from the sides of the tube. Since the engines and
electrical generating power will be on the ground you could create
quite large plasmas and E/M fields.
You could even use nuclear engines since they will stay on the ground
as long as you use the type that does not radiate the fuel.
You could send up just hydrogen gas or liquid and ignite it on exiting
the vents.
Or you could use the idea of just the fluid pressure alone providing
the propulsive force.
Bob Clark
Robert Clark wrote:
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground [you
> may need to use a fixed-width font such as Courier New to properly
view
> the diagram.]
> A key aspect of the proposal as desccribed below is that the
material
> forming the pipeline does not have to be especially strong as for
> example to support its own weight. The force for supporting each
> portion of the pipeline is provided by the thrust produced by
> pressurized fluid vented along the entire length of the pipeline.
> Note that this also would provide a means of producing a space tower
> or space elevator (to low Earth orbit). You really wouldn't need to
> attach a rocket to the end of the rocket itself. You would use the
> pipeline to *slowly* raise the payload to the required altitude for
> LEO. Then you could use a rocket attached to the payload only to give
> the payload the required tangential orbital velocity. Note that the
> fuel and rocket that would need to be attached to the payload would
be
> significantly less since this fuel would not be used for getting it
up
> to altitude.
> You could have this "space fountain" raised only when you wanted to
> launch a payload, or you could have it permanently raised in the air.
> This would work if you located the fountain next to a large
permanently
> flowing source of water such as a river. Then for example a ram pump,
> which requires no moving parts, could be used to raise the water in
the
> fountain:
>
> Contents for the pulser pump section of Gaiatech.
> http://members.tripod.com/~nxt wave/gaiatech/pulser/index.htm
>
> Designing a Hydraulic Ram Pump.
> http://www.lifewater.org/resources/rws4/rws4d5.htm
>
>
> Bob Clark
>
>
>
**********************************************************************************
> Newsgroups: sci.astro, sci.physics, sci.mech.fluids, sci.engr.mech,
> sci.space.policy
> From: rgregorycl...@yahoo.com (Robert Clark)
> Date: 20 Nov 2004 17:04:01 -0800
> Local: Sat, Nov 20 2004 5:04 pm
> Subject: Re: "Rockets not carrying fuel" for orbital transfer.
>
>
>
> "George Dishman" <george.dish...@clara.co.uk> wrote in message
> <news:11005508...@damia.uk.clara.net>...
> > "Robert Clark" <rgregorycl...@yahoo.com> wrote in message
> > news:832ea96d.04111...@posting.google.com...
> > >...
>
>
> > > I came up with two other ideas for reducing the weight of the
fluid
>
> > > that had to be supported by the rocket as the tube trails behind
> the
> > > rocket.
> > > Firstly, I wanted to investigate both the possibilities of using
> > > gaseous hydrogen or liquid hydrogen for the fluid carried by the
> tube.
>
>
> > That drops the density so you need much higher
> > speeds for the same flow rate so makes everything
> > more difficult.
>
>
> > > However, the liquid hydrogen scenario just gave too much weight.
> But
> > > suppose the rocket didn't have to provide the propulsion for the
> fluid
> > > in the tube? This is what I envision:
>
>
> > <Snip pictures>
>
>
> > All you have done is use a compound engine. The
> > same mass is being accelerated to the same speed
> > so will need the same fuel. You are forgetting
> > the engines not only lift the craft but also the
> > fuel needed to lift themselves. In fact with more
> > engines, you have greatly increased the mass and
> > the fuel needed, and all these schemes create a
> > huge drag with air friction on the tube which also
> > needs more fuel.
>
>
> > Instead, imagine using a nearly rigid pipe as the
> > arm of a trebuchet to pump fuel only over the first
> > few seconds. That might be practical though the
> > risks during disconnection are significant.
>
>
> > George
>
> I'm also investigating the possibility of using a rigid structure to
> reach into LEO. However, I think the efficiency of the tube method is
> better than you suggest.
> Let's go back to the case of launch from Earth to LEO. I'm still
> considering here that you're not using engines to combust fuel but
are
> only conducting a high pressure fluid up the tube to provide
> propulsion. So the weight of the exhaust ports is quite small, not
> that of a full blown engine.
> Let's estimate the the size of these exhaust ports.
>
>
> ^
> |
> |
> Towards the rocket.
>
>
> | |
> | |<----Fluid carrying tube.
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\
> // | | \\
> | |
> | |
> | |
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\<---Exhaust ports directed aft.
> // | | \\
> | |
> | |
> | |
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\
> // | | \\
> | |
> | |
> | |
>
>
> Let's say you put a pair of these ports every 100 meters. Then each
> pair of ports would only have to provide the thrust to support the
> weight of 100 meters of the tube and fluid. Let's use liquid hydrogen
> now. Its density is 71 kg/m^3. The volume of a 100 m tube, .3m wide
is
> Pi*(.15)^2*100 = 7.07 m^3. So the mass is 71 kg/m^3 times this or
> about 502 kg, 1104 lbs.
> We're still using the presumption that we can communicate, say, a
> pressure like the 6400 psi pressure produced by the shuttle liquid
> hydrogen turbopumps up the tube. (Whatever type of pumps we use would
> be located on the ground not the rocket so can be quite large.) Now
we
> want two exhaust ports to support 1104 lbs., or 552 lbs. each. So 552
> lbs = (pressure)*(square area of ports) = 6400 * Pi * (1/4)*(diameter
> of ports)^2 . We get a diameter of .33 in or 8 millimeters. Actually
> they might even be smaller than this by using convergent-divergent
> type nozzles used with rockets.
> Now remember the entire tubes weight is supported by these exhaust
> ports so the great majority of the fluid that reaches the rocket will
> be driving only the payload and rocket. For a .3m = 12in wide tube
> this could be a thrust of 6400 * Pi * 6^2 = 723,824 lbs. that is
> solely used to loft the payload and (engineless) rocket, and again we
> can probably do better than this using the nozzles normally used on
> rockets.
> Note that we can get even more thrust from the exhaust ports by
> making them wider or by using more than 2 at each level. This is
> important since we can also solve the hypersonic drag problem. These
> exhaust ports are not engines but it would be a simple (and light
> weight matter) to give them directional ability. Then you could have
> them automatically direct their thrust to counteract the drag caused
> by each portion of the tube.
>
>
> Bob Clark
>
**********************************************************************************
Don A. Gilmore
news:1112250636....@o13g2000cwo.googlegroups.com...
It's remarkable the number of ways this can be implemented, and all
are doable with currently available tech.
You could for example use shuttle or Saturn V type engines on the
ground and direct the exhaust through the tubes upwards. These engines
have exhaust velocities in the range of 4000m/s. A particle sent upward
at this initial speed (ignoring atmosphere) could reach 800 km.
At 100 km it would have a speed above 3700m/s, though the tube of course
induces frictional effects which will reduce this speed somewhat.
--
Whoa! You're going to have to show your math on that one.
Don
Kansas City
Ian Stirling
> Earl Colby Pottinger <ear...@idirect.com> wrote in
> news:oKGdnWBjp4n...@look.ca:
>
>> For standard temperature 0C or 273K the root mean square speeds are:
>> * hydrogen 1846 m/s
>> * nitrogen 493 m/s
>> * oxygen 461 m/s
>>
>> At 3000K I get
>> * hydrogen 6116 m/s which is a good exhaust speed above that of most
>> chemical rocket designs.
>
> Nitrogen might be a good 'non poluting' reaction mass.
Not really.
Lousy atomic mass, diatomic, so you waste energy splitting it, and you
get nitrogen oxides when it hits the atmosphere at Km/s.
Ian Stirling
> In article <1112078175....@z14g2000cwz.googlegroups.com>,
> Matt <mam...@gmail.com> wrote:
>>As for fuelless rockets, why didn't the mass driver ever go anywhere.
>>Granted anything you launch in it has to be able to withstand seriously
>>extreme acceleration, but we could keep some rockets for the sensitive
>>stuff and launch all the bulk into orbit with the mass driver...
>
> The idea isn't ridiculous, but it's tricky to make it work well on Earth's
> surface, where payloads have to punch out through the atmosphere. The
To put vague numbers on this - to make a survivable (not pleasant)
launcher to launch humans, you need some hundreds of tons per square
meter of density for your payload capsule, to stop it slowing down
at unsurvivable rates.
Very large capsules only, and hence huge powers.
(not to mention the extreme hypersonic shock footprint)
For small capsules, it's really hard to get a useful fraction of
orbital velocity, even if you're willing to scrub off a lot of speed.
This tends to mean that instead of the ideal of launching a payload
which has orbital velocity, and perhaps requiring a tiny rocket
to circularise the orbit, you end up exiting the atmosphere at a
rather low speed, and then needing to get to orbital speed - but with
the added mass of beefing up the structure to cope with aerodynamic and
heating loads low in the atmosphere.
So your payload doesn't look like a tin can with a tiny rocket on, but
a multi-stage rocket with heavy heatshielding, all fired out of the gun.
It's not a clear win, and some argue that when you optimise for whole
system costs, the electromagnetic launcher component of the initial
velocity comes out at 0.
bz
news:424c18af$0$42304$ed26...@ptn-nntp-reader02.plus.net:
Good points. Hence my 'might'. I was thinkin out loud. :)
Robert Clark
I'm using the formulas for the distance and velocity for a body given
an initial velocity upwards when you neglect air resistance:
1.) s = v0*t - 1/2*g*t^2 , and 2.) v = v0-g*t.
If you set the initial speed v0 = 4000m/s, then when it reaches it's
greatest height v = 0 = 4000 - 10* t, so t = 400s. Plug this into the
equation 1.), to get s = 800,000m or 800km.
To confirm the 3700m/s speed at 100 km, find how long it takes for the
speed to reduce to 3700m/s: v = 3700 = 4000 - 10*t, so t = 30s. Then s
= 4000*30 - 1/2*10*30^2 = 115000m or 115km.
However, saying the speed is reduced "somewhat" by frictional effects
by the gas flowing through the 100km long tube is probably an
understatement.
There was some discussion on how this might be calculated on this
thread with no firm conclusion on what it would be:
Newsgroups: sci.astro, sci.physics, sci.mech.fluids, sci.engr.mech,
sci.space.policy
From: rgregorycl...@yahoo.com (Robert Clark)
Date: 7 Nov 2004 07:44:30 -0800
Local: Sun, Nov 7 2004 7:44 am
Subject: Question about Poiseuille's formula.
http://groups-beta.google.com/group/sci.astro/browse_frm/thread/faf96e76704b8593/
Bob Clark
David Wilkinson
Getting the apostrophe wrong above is unfortunately typical of your
approach which always involves fundamental mistakes. You can't neglect
air resistance so the rest of the analysis is irrelevant.
Your original "vertical pipe supported by gas jets" idea neglected the
weight of the pipe, which easy to estimate at about 50 times that of the
gas inside it, so it has no chance at all of working.
Robert Clark
> "Don A. Gilmore" wrote:
> >
> > news:42487FF4...@hate.spam.net...
> > > Robert Clark wrote:
> > > >
> > > > I copied below a proposal for space access where the
propulsion is
> > > > provided by a highly pressurized fluid piped up from the ground
[you
> > > > may need to use a fixed-width font such as Courier New to
properly view
> > > > the diagram.]
> > > > A key aspect of the proposal as desccribed below is that the
material
> > > > forming the pipeline does not have to be especially strong as
for
> > > > example to support its own weight. The force for supporting
each
> > > > portion of the pipeline is provided by the thrust produced by
> > > > pressurized fluid vented along the entire length of the
pipeline.
> > >
> > > What percentage of the inflow makes it to the top, git? What is
the
> > > weight of a 50-mile depth of liquid oxygen, git?
> >
> > Not to mention pressure.
>
> I did - that is the weight of the column/area. Gonna cost ya dear in
> mgh, PV, cone fittings, and foot-thick walled piping at the bottom.
> Cryogenic metal loses strength. Vacuum insulation does poorly in
>
> (1 cm)(1 cm)(50 miles)(5280 feet/mile)(12 in/ft)(2.54 cm/in)(1.14
> g/cm^3)(0.0022046 pounds/gram)(6.4516 cm^2/in^2) = 130,473 psi plus
> static compression of the liquid.
>
> high pressure environments. And you have to fill the pipe before
> anything in becomes something out. Not only is it a stooopid idea,
it
> is a stooopid Fermi idea.
>
Pumps already exist that can produce pressures in the 100,000 psi to
200,000 psi range:
Air Driven Liquid Pumps.
"Haskel air driven pumps offer many advantages over conventional
electrical driven units as follows:
Ability to stall at any predetermined pressure and hold this fixed
pressure without consuming power or generating heat.
No heat, flame or spark risk.
Infinitely variable cycling speed output.
Up to 100,000 psi (7,000 bar) pressure capability with special units to
150,000 psi (10,000 bar)."
http://www.flw.com/haskel/1.htm
FC SERIES(TM)
High Pressure Pumps
"The FC SERIESTM pumps are available for pressures from 10,000 to
200,000 psi, and 10 to 200 hp."
http://www.hydropac.com/HTML/FCseries.html
Böhler High-Pressure Technology: pumps for tough situations.
"Apart from these high-pressure and ultra high-pressure pumps with a
maximum pressure of 10,000 bar, the company, in the Austrian province
of Styria, also manufactures tube reactors, coolers and valves for
high-pressure and ultra high-pressure applications in the chemical
process engineering sector."
http://www.parker.waaps.com/lit_page.php?page=743&id=99
These could easily be scaled to provide 100's of liters per second
rather than the liters per minute they now provide. (Or you could use a
whole lot of the little ones.)
For a liquid at least, you could get the required extra pressure out
at the top of the tube by adding this amount to the pressure provided
by the pumps. So if 100,000 psi on the ground gave you the liquid
reaching the top of the tube, 106,000 psi on the ground gives you the
liquid at 6000 psi reaching the top of the tube.
Carbon fibers are already in industrial use that greatly exceed this
strength requirement in tension for the tube:
Carbon fiber (Dani Eder)
"Currently 1 million psi carbon fiber (as in Amoco T1000) is the
highest strength. According to their representatives, they can
probably get 1.1 to 1.2 million psi in a production fiber if anyone
needs enough of it to get them to
go through the job of setting up a production line for it."
http://yarchive.net/space/exotic/carbon_fiber.html
I mentioned using a liquid but this was mostly because they are
incompressible and it is easier to calculate the pressures that would
be required. Since gases are much lighter it may be better to use a gas
rather than a liquid. This would result in much reduced pressure
requirement for the pumps on the ground.
Rather than using electrically driven commercial pumps as mentioned
above I much prefer the idea of using gravity-driven flowing-water
based pumps (which could pump either a liquid or gas.) These require
no external energy to operate, only a source of flowing water.
Brian White the inventor of the "pulser pump" wants me to mention his
pump is actually different than the "hydraulic ram pump" and requires
no moving parts, while the hydraulic ram pump actually requires a set
of valves to operate.
How the pulser pump works, benefits to the environment, and details
about how much you can pump.
"You can pump :
Liters per minute = Head X lpm at dam ÷ vertical height X 0.1"
http://members.tripod.com/~nxtwave/gaiatech/pulser/detailed.htm
This equation shows the height pumped can be arbitrarily high with a
proportional reduction in the amount of fluid delivered.
Glockemann RAM Pump Details.
http://www.rpc.com.au/products/pumps/glockemann/glockemann.html
The table on this page shows the specifications for a ram pump that
can pump to a height up to 200 times the fall height of the water. So a
river or stream with a fall of 500 meters could pump to a 100km height.
Another possibility for a pump might be to use the principle of a
hydraulic lift. As shown on this page a large diameter piston moving a
short distance can move a thin diameter piston a long distance via an
incompressible fluid:
How Hydraulic Machines Work
http://science.howstuffworks.com/hydraulic1.htm
To drive the liquid upwards to 100km you would need to lower quite a
large weight onto the large piston. For example there are locomotives
that weigh over 1 million pounds. You could drive one or more of these
up a 500 meter hill then onto the large piston. The liquid would move
up the thin tube to 100km as long as the ratio of the cross-sectional
areas of the tube and large piston is similarly 1 to 200.
Bob Clark
Robert Clark
> > I'm using the formulas for the distance and velocity for a body
given
> > an initial velocity upwards when you neglect air resistance:
> >
> > 1.) s = v0*t - 1/2*g*t^2 , and 2.) v = v0-g*t.
> >
> > If you set the initial speed v0 = 4000m/s, then when it reaches
it's
> > greatest height v = 0 = 4000 - 10* t, so t = 400s. Plug this into
the
> > equation 1.), to get s = 800,000m or 800km.
>
> Getting the apostrophe wrong above is unfortunately typical of your
> approach which always involves fundamental mistakes. You can't
neglect
> air resistance so the rest of the analysis is irrelevant.
>
> Your original "vertical pipe supported by gas jets" idea neglected
the
> weight of the pipe, which easy to estimate at about 50 times that of
the
> gas inside it, so it has no chance at all of working.
>
For the fluid moving inside the pipe you can neglect *air* resistance
assuming your fluid is not *air*. What will be significant will be the
frictional and viscosity effects of the fluid moving in the pipe.
In the first post I showed that liquid hydrogen at 71 kg/m^3 density
would weigh 512kg in each 100 meter portion of a .3m wide pipe. I
showed the exhaust vents in each 100 meter portion could support this
weight.
Using currently available carbon fiber for the tube material, its
density is 1600 kg/m^3. Even if you made the pipe 1 cm thick the volume
of the pipe material itself for a 100 meter long hollow pipe would be
.01 x 3.14 x .3 x 100 = .942 m^3, so would weigh 1507 kg. So you just
make the vents twice as wide to produce 4 times as much thrust.
But it is unlikely you'll have to make the pipe this thick. Carbon
fiber is stronger than steel. You might get by with the pipe 1 mm
thick, especially if you used much lighter gases rather than liquids.
Then the mass of the 100 meter portion of the pipe would be only 150
kg.
Bob Clark
Jonathan Barnes
> I'm using the formulas for the distance and velocity for a body given
> an initial velocity upwards when you neglect air resistance:
>
> 1.) s = v0*t - 1/2*g*t^2 , and 2.) v = v0-g*t.
>
> If you set the initial speed v0 = 4000m/s, then when it reaches it's
> greatest height v = 0 = 4000 - 10* t, so t = 400s. Plug this into the
> equation 1.), to get s = 800,000m or 800km.
> To confirm the 3700m/s speed at 100 km, find how long it takes for the
> speed to reduce to 3700m/s: v = 3700 = 4000 - 10*t, so t = 30s. Then s
> = 4000*30 - 1/2*10*30^2 = 115000m or 115km.
> However, saying the speed is reduced "somewhat" by frictional effects
> by the gas flowing through the 100km long tube is probably an
> understatement.
> There was some discussion on how this might be calculated on this
> thread with no firm conclusion on what it would be:
Steam pipe practice.... MAX velocity 100 m / sec
We are talking runs of pipe under 100m long
Your going to need a pipe with several METERS thick steel walls to hold your
pressures.
Lets put things in perspective... take a 1/2m diameter steam pipe, stainless
steel, 50mm wall
Weight per metre, 573 Kg, so that's 57,300 tons for a 100 Km pipe.
Lets have just a 100 meter run and hustle some steam down it.... 7 bar inlet
pressure.
For a one bar ( 14.7 PSI ) pressure loss over the length, the entry speed
would be 52 m/s
GET REAL
you are orders of magnitude away from what it is possible.
--
Jonathan
Barnes's theorem; for every foolproof device
there is a fool greater than the proof.
To reply remove AT
eromlignod
weight of fluid in the pipe? If your pump is capable of producing 100
kpsi and your column of fluid is gravitationally producing a pressure
of 100 kpsi, your not going to pump anything anywhere.
Don
Kansas City
David Wilkinson
A few other things he may have overlooked:
What about stability of the pipe under gravity? There is this thin pipe
hundreds of meters tall going up into the sky. Even if the jets could
support its weight what is to stop it just toppling over sideways?
A high velocity stream through a thin pipe will probably make it whip
around.
What is the strength of carbon fibre pipe at cryogenic temperatures?
Why won't the hydrogen heat up and boil off, when its boiling point at
atmospheric conditions is about -255C.
As well as the weight of the pipe, what about the weight of the
insulation trying to keep the hydrogen liquid? That has to be supported
as well.
How is he going to get the pipe from horizontal at the start with no
flow through it to vertical in operation with full flow. There won't be
any chance to build it up gradually by adding lengths of pipe when it is
all at thousands of psi pressure and cryogenic temperatures.
Why does he not just stick to science fiction, where this proposal
belongs. Things don't have to really work in stories :-)
Bryan Derksen
<octob...@alexanderpics.com> wrote:
>"Matt" <mam...@gmail.com> wrote in message
>news:1112078434.5...@o13g2000cwo.googlegroups.com...
>> Ditto, but while Mars would save us from an asteroid, we'll have to be
>> a bit further away to avoid any nearby nova, supernova, x-ray burst,
>> etc. or even an especially bad solar flare from our own sun.
>
>Would hiding inside an asteroid protect you from those?
Why go so far away when not only is there plenty of rock for shielding
right here on Earth, but also a great deal of infrastructure and life
support supplies that would survive even if surface life didn't? Good
old mine shaft habitats should be proof against pretty much anything
that doesn't physically destroy them.
Bryan Derksen
dlzc1 D:cox T:n...@nospam.com> wrote:
>Dear Mike Rhino:
>> Would hiding inside an asteroid protect you
>> from those?
>
If the alternative is dying I think I'd rather make do with a cave.
With the right lighting and decor it could probably be made quite
pleasant; many people spend large portions of their lives indoors
already without going nuts about it. And if it's a multi-generation
thing the kids will grow up thinking it's perfectly normal to live
underground.
David M. Palmer
(in article <md2s415r0l08khvuu...@4ax.com>):
A quick survey would have to be made of all the available mine sites in the
country. But I would guess... that ah, dwelling space for several hundred
thousands of our people could easily be provided.
A computer could be set and programmed to accept factors from youth, health,
sexual fertility, intelligence, and a cross section of necessary skills. Of
course it would be absolutely vital that our top government and military men
be included to foster and impart the required principles of leadership and
tradition.
Naturally, they would breed prodigiously, eh? There would be much time, and
little to do. But ah with the proper breeding techniques and a ratio of say,
ten females to each male, I would guess that they could then work their way
back to the present gross national product within say, twenty years.
You might ask: wouldn't that necessitate the abandonment of the so called
monogamous sexual relationship, I mean, as far as men were concerned?
Regrettably, yes. But it is, you know, a sacrifice required for the future of
the human race. I hasten to add that since each man will be required to do
prodigious... service along these lines, the women will have to be selected
for their sexual characteristics which will have to be of a highly
stimulating nature.
dlzc1 D:cox T:net@nospam.com N:dlzc D:aol T:com (dlzc)
"David M. Palmer" <dmpa...@email.com> wrote in message
news:0001HW.BE744790...@news.speakeasy.net...
Been done. See "A Boy and His Dog." And put your pants back on!
;>)
David A. Smith
Tom Potter
"Alain Fournier" <alai...@sympatico.ca> wrote in message
news:ZUk2e.7556$w63.6...@news20.bellglobal.com...
>
>
> Henry Spencer wrote:
> > In article <NC12e.19$45....@news.uchicago.edu>,
> > <mme...@cars3.uchicago.edu> wrote:
> >
> >>>If you wanted to send energy to a rocket, you would be better off with
a
> >>>laser. ... The fuel tank would contain ammonia and nothing else.
> >>>The back of the rocket would have a concave mirror that concentrates
the
> >>>laser light on one spot. Ammonia would be sent to that spot, heat up,
and
> >>>be ejected as exhaust.
> >>
> >>And the advantage over "something that burns" would be? I mean other
> >>than saying "I'm high tech, I'm using a laser":-)
> >
> >
> > 1. You can raise the exhaust gas to higher temperatures -- giving more
> > energy to be converted into exhaust kinetic energy -- if you aren't
> > limited by the energy content of chemical fuels.
>
> rockets. Does this mean that laser rockets would have to have
> either exhaust temperatures similar to chemical rockets, or
> have very low thrust à la ion engine rockets?
The maximum efficiency of a rocket engine,
occurs when the exhaust velocity equals the rocket velocity.
The most efficient rocket engine,
would be one that used an energy source,
to modulated the exhaust velocity
of a mass source.
The energy source would not have to be
mounted on the vehicle.
--
Tom Potter
http://home.earthlink.net/~tdp
Robert Clark
The weight of the fluid and of the tube is being supported by the high
pressure or high velocity fluid being directed aft from vents along the
entire length of the tube.
As for the thickness of the tube, this page gives a commonly used
formula for calculating the thickness of pipe required to hold a given
fluid pressure, called Barlow's formula:
Barlow's Formula Calculator.
http://www.texaspipe.com/barlows_formula.html
The formula is:
P=2St/D, where P is the pressure in the pipe, S is the tensile
strength, t is the thickness, and D is the inner diameter of the pipe.
So t = PD/2S.
Then for carbon fiber with tensile strength of 1,000,000 psi and with
a pressure in the tube of 100,000 psi, a 1 cm thick tube would suffice
for a tube with an inner diameter of 20 cm.
Keep in mind though that the pressure would likely be less than this
if we used the less dense gases rather than liquids for the fluid.
Bob Clark
Robert Clark
At least for liquids if 100,000 psi gets you to the top of the 100km
column, then 106,000 psi gets you to the top with a pressure of 6000
psi.
Pumps exist that can pump pressures twice this.
Bob Clark
Robert Clark
Note that I originally said let the vents be placed at 100 meter
intervals, but you could change this to have greater control of the
position and orientation of the pipe. From the calculation quite thin
vents could support 100 meters, so even smaller ones would be required
for shorter intervals between the vents.
These vents are to be designed to direct the fluid in the opposite
direction to gravity and drag which is easy to do technically with
accelerometers.
The fluid stream does not necessarily have to be high velocity. It
could be just high pressure. In any case the vents automatically orient
to keep the pipe vertical.
The fluid does not have to be cryogenic hydrogen. It could be gas.
You can start the tube rising slowly at the start. Remember each
portion of the tube is supported by the exhaust vents in that portion
David Wilkinson
It sounds more like the Indian Rope Trick than a serious enigineering
proposal.
Try it in your garden with a hose pipe.
David Summers
inherent danger and power wasted by a tower held up using thrust.
Just make a single section capable of taking a LOT of fuel, pumping
99.7% up 10 meters, and use the remaining 0.3% in a rocket engine (Isp
of 450, in this example). You could build a tower like this - it would
just use as much propellant as continual space shuttle launches with
really accomplishing anything!
Jonathan Barnes
From: "Robert Clark" <rgrego...@yahoo.com>
> > > To confirm the 3700m/s speed at 100 km,
( inapplicable formula used gas in a pipe is not a solid body )
> >
> > Steam pipe practice.... MAX velocity 100 m / sec
> >
> > We are talking runs of pipe under 100m long
> >
> > Your going to need a pipe with several METERS thick steel walls to
> hold your
> > pressures.
> >
> > Lets put things in perspective... take a 1/2m diameter steam pipe,
> stainless
> > steel, 50mm wall
> >
> > Weight per metre, 573 Kg, so that's 57,300 tons for a 100 Km pipe.
> >
> > Lets have just a 100 meter run and hustle some steam down it.... 7
> bar inlet
> > pressure.
> >
> > For a one bar ( 14.7 PSI ) pressure loss over the length, the entry
> speed
> > would be 52 m/s
> >
>
> The weight of the fluid and of the tube is being supported by the high
> pressure or high velocity fluid being directed aft from vents along the
> entire length of the tube.
> As for the thickness of the tube, this page gives a commonly used
> formula for calculating the thickness of pipe required to hold a given
> fluid pressure, called Barlow's formula:
>
> Barlow's Formula Calculator.
> http://www.texaspipe.com/barlows_formula.html
>
> The formula is:
>
> P=2St/D, where P is the pressure in the pipe, S is the tensile
> strength, t is the thickness, and D is the inner diameter of the pipe.
> So t = PD/2S.
>
> Then for carbon fiber with tensile strength of 1,000,000 psi and with
> a pressure in the tube of 100,000 psi, a 1 cm thick tube would suffice
> for a tube with an inner diameter of 20 cm.
> Keep in mind though that the pressure would likely be less than this
> if we used the less dense gases rather than liquids for the fluid.
>
>
> Bob Clark
>
Carbon fibre and carbon fibre laminate are different...
A binder is needed to hold the fibre. ( and stopping the gas leaking :-) )
Your pipe formula is for non directional materials. carbon laminates would
be directional.
100,000 PSI.... = 6,800 bar, air density at STP 1.2 Kg /m^3... hydrogen
density 0.042 ( is H monatomic ? )
Hydrogen at 6,800 bar, density 280 kg /m^2 ( twice this if diatomic )
100 Km high column static pressure = 2750 bar.
At the speeds you are considering gas friction will vaporise the pipe
material.
Ignoring the vaporisation of the pipe :-)
Assume a loss of ( 6800 - 2750 ) / 1000 = 4 bar / 100 m a speed of 120 m/s
is closer to your gas speed.
Loss should rise with the square of velocity, so a loss of 53000 psi per
100m at 3600 m/s would be expected...
of course the formulas would be way outside their valid zones, and would
under estimate the loss.
GET REAL
You are orders of magnitude away from the possible.
Jonathan Barnes
diatonic )
> 100,000 PSI.... = 6,800 bar, air density at STP 1.2 Kg /m^3... hydrogen
> density 0.042 ( is H monatomic ? )
>
> Hydrogen at 6,800 bar, density 280 kg /m^2 ( twice this if diatomic )
> 100 Km high column static pressure = 2750 bar.
Hydrogen density at STP = 0.0899 kg/m^3 so at 6800 bar it's density is 610
Kg /m^3
If... ( unallowable ) we ignore pressure and density variations in the 100
km pipe we would have a static pressure drop of DgH Pascal's
610 x 9.81 x 100000 = 600 MP = 6000 Bar = 82000 psi.
George Dishman
"Jonathan Barnes" <jbar...@btinternet.com> wrote in message
news:d2oeb2$kt6$1...@sparta.btinternet.com...
> Correcting my last post.... Hydrogen density at STP = 0.0899 kg/m^3 (
> diatonic )
>
>> 100,000 PSI.... = 6,800 bar, air density at STP 1.2 Kg /m^3... hydrogen
>> density 0.042 ( is H monatomic ? )
>>
>> Hydrogen at 6,800 bar, density 280 kg /m^2 ( twice this if diatomic )
>> 100 Km high column static pressure = 2750 bar.
>
>
> Hydrogen density at STP = 0.0899 kg/m^3 so at 6800 bar it's density is
> 610
> Kg /m^3
>
> If... ( unallowable ) we ignore pressure and density variations in the 100
> km pipe we would have a static pressure drop of DgH Pascal's
> 610 x 9.81 x 100000 = 600 MP = 6000 Bar = 82000 psi.
Don't you also have to consider that the
purpose is to accelerate the rocket hence
some additional pressure is needed to
accelerate the mass of the fuel up the
pipe and accelerate the mass of the pipe
itself.
George
Robert Clark
written by an engineer that contains the calculated strengths of some
theoretical materials:
Hanging Tough.
"Perfect diamond is a another real material, but there is a theoretical
material which is far stronger. It, too, uses carbon, but in the form
of benzine-like rings. These are looped through each other in a
three-dimensional matrix, and the impressive figures (1.0 X 10^15
(that's a 1 followed by 15 zeroes), 9.3 X 10^14, and 9.3 X 10^12
N/cm^2) for the yield strengths come from the fact that not only is
deformation resisted by the normal molecular bonds, but by the mutual
repulsion of the shared electron clouds around the rings. As you can
imagine, this also makes the material extremely rigid. And hard. (My
thanks to Dr. John Brantley for telling me about this.)"
http://www.dcr.net/~stickmak/JOHT/joht10strength.htm
Anyone know anymore about this theoretical material of John
Brantley's?
(BTW, I was puzzled by some of the strength numbers here initially but
the author is giving them in terms of N/cm^2 instead of N/m^2, which is
the pascal. To get the numbers in pascals, multiply by 10,000.)
Bob Clark
Dwayne
Jonathan Barnes
"George Dishman" <geo...@briar.demon.co.uk> wrote in message
news:d2ofgh$bkd$1...@news.freedom2surf.net...
it, AND it's venting enough hydrogen to support itself ... BIG flares along
the section in the atmosphere, AND pressure loss is ignored... ETC...
ETC.... ETC..
the problem of actually having a rocket on the top struck me as so trivial
it could safely be ignored.
Beside I was dealing with pressure *loss*, not total pressure. the OP was
thinking of a starting pressure of 6800 bar, the maximum his pipe was
(miss)designed for so a top pressure of 800 bar ( I don't think so :-) )
--
Robert Clark
The strength of this material is FAR greater than even carbon
nanotubes:
Hanging Tough.
"Perfect diamond is a another real material, but there is a theoretical
material which is far stronger. It, too, uses carbon, but in the form
of benzine-like rings. These are looped through each other in a
three-dimensional matrix, and the impressive figures (1.0 X 10^15
(that's a 1 followed by 15 zeroes), 9.3 X 10^14, and 9.3 X 10^12
N/cm^2) for the yield strengths come from the fact that not only is
deformation resisted by the normal molecular bonds, but by the mutual
repulsion of the shared electron clouds around the rings. As you can
imagine, this also makes the material extremely rigid. And hard. (My
thanks to Dr. John Brantley for telling me about this.)"
http://www.dcr.net/~stickmak/JOHT/joht10strength.htm
He's giving these in N/cm^2 remember; so in pascals you would multiply
these by 10,000. Then this material is claimed to have a strength in
tension and compression of 10 billion gigapascals! The largest quoted
strength I've seen for carbon nanotubes is 160 gigapascals.
I wonder if he made a mistake and the numbers he was given for this
material were actually already in pascals, N/m^2. Even then that would
mean a strength of 1 million gigapascals.
To put this is in perspective such a material could be used to build
both a space elevator and space tower to geosynchronous orbit WITH NO
TAPER!
Bob Clark
dlzc1 D:cox T:net@nospam.com N:dlzc D:aol T:com (dlzc)
"Robert Clark" <rgrego...@yahoo.com> wrote in message
news:1112548740.3...@z14g2000cwz.googlegroups.com...
Or interlock the rings to form a cloth (think chain link), roll
the cloth to form a fiber... still a pipe dream.
David A. Smith
Bryan Derksen
<dmpa...@email.com> wrote:
>A quick survey would have to be made of all the available mine sites in the
>country. But I would guess... that ah, dwelling space for several hundred
>thousands of our people could easily be provided.
It will also help if the "radiation pulse" phase is short but the
"toxic surface environment" phase lingers long afterward, the
underground habitats can be packed pretty tight to serve as temporary
habitats and then more spacious airtight surface dwellings moved into
afterward.
>A computer could be set and programmed to accept factors from youth, health,
>sexual fertility, intelligence, and a cross section of necessary skills. Of
>course it would be absolutely vital that our top government and military men
>be included to foster and impart the required principles of leadership and
>tradition.
I wouldn't trust a computer with any decision-making other than random
"lotteries" among equally-qualified human-selected candidates,
personally. It almost goes without saying that a disproportionate
number of "important people" will arrange to be in the shelters when
disaster hits, but I suspect their importance among the survivors will
diminish soon afterward; they got to their current positions with a
skill-set that won't necessarily serve them as well under such
different circumstances, and they'll be missing most of the leverage
they had previously (unless large chunks of the rest of the population
is selected specifically to maintain that, I suppose. Details will
vary and I presume every major country or large organization will be
setting up survival habitats independantly).
>Naturally, they would breed prodigiously, eh? There would be much time, and
>little to do. But ah with the proper breeding techniques and a ratio of say,
>ten females to each male, I would guess that they could then work their way
>back to the present gross national product within say, twenty years.
The limit on growth in a difficult environment like this isn't going
to be child _bearing_ resources, it's going to be child _rearing_
resources (and also habitat infrastructure expansion capabilities,
especially if the surface remains uninhabitable in the long term). I
realize you're going for a Dr. Strangelove riff here but it just
doesn't strike me as a realistic approach. In fact, IIRC in real-world
marginal environments where survival is very hard, low-tech human
cultures tend towards polyandrous systems where several men (often
closely related) band together to support one woman and their children
with her.
Bryan Derksen
<rgrego...@yahoo.com> wrote:
> It's remarkable the number of ways this can be implemented, and all
>are doable with currently available tech.
The rocket-supported tower doesn't seem to be very well-recieved here.
How about one supported by electromagnetic mass drivers instead?
http://en.wikipedia.org/wiki/Space_fountain
The space fountain concept uses a closed circuit of iron pellets
travelling up and down through the tower to provide support. Most of
the tower can even be omitted above the atmosphere where the vacuum is
strong enough for the pellets to travel without significant friction,
the elevator cars coupling directly to the pellet stream for lift.
Dwayne
news:ect0511tdspa1etof...@4ax.com...
Same crap, different pile.
Dwayne
Dale Trynor
Dale Trynor wrote:
You guys are getting nowhere practical and I had to jump in and help.
Did some posts quite some time ago on the idea of a pneumatic tower and
it was along the idea of building really tall towers out of pressurized
tanks. What was interesting is that if you could make the tanks equally
buoyant to the surrounding air you would have almost no limit to how
high you could go and still stay within the comparatively cheap or at
leas by comparison to the alternatives.
This gets to be too much of a discussion for my ambition right now so
why doesn't someone here try some engineering and mathematics for some
ideas for this idea.
Some approximations to get you started. Every 3.5 miles straight up the
air pressure is 1/2. So a 9 mile high tower would have an atmospheric
pressure of about 3.25 psi and a 9 mile high tower would be about 1.65 psi.
This gets to be a rather useful thing for mass drivers because the whole
tube can be evacuated to a partial vacuum without a massive door at its
upper end.
Another use for a really high low cost tower is the temperature
differences one can get with emissive cooling at the top of such a
tower, gets really useful for energy generation.
Gaseous ammonia goes up and comes down as liquid giving you quite a good
closed cycle hydroelectric plant.
Dale
Russell Wallace
> After looking up references to strong materials I found this web page
> written by an engineer that contains the calculated strengths of some
> theoretical materials:
>
> Hanging Tough.
> "Perfect diamond is a another real material, but there is a theoretical
> material which is far stronger. It, too, uses carbon, but in the form
> of benzine-like rings. These are looped through each other in a
> three-dimensional matrix, and the impressive figures (1.0 X 10^15
> (that's a 1 followed by 15 zeroes), 9.3 X 10^14, and 9.3 X 10^12
> N/cm^2) for the yield strengths come from the fact that not only is
> deformation resisted by the normal molecular bonds, but by the mutual
> repulsion of the shared electron clouds around the rings. As you can
> imagine, this also makes the material extremely rigid. And hard. (My
> thanks to Dr. John Brantley for telling me about this.)"
> http://www.dcr.net/~stickmak/JOHT/joht10strength.htm
I'm neither a chemist nor a mechanical engineer, so someone correct me
if I'm wrong, but as far as I can see the above is equivalent to saying:
"Steel chains are far stronger than steel bars, because the impressive
figures for the yield strengths come from the fact that not only is
deformation resisted by the normal metallic bonds, but by the mutual
repulsion of the electron clouds around the iron atoms where the links
press on each other."
In other words, the error is in thinking that breaking the structure
requires forcing the rings into each other, whereas it actually only
requires breaking the rings.
--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.
Bryan Derksen
>"Bryan Derksen" <bryan....@shaw-spamguard.ca> wrote in message
>news:ect0511tdspa1etof...@4ax.com...
>> How about one supported by electromagnetic mass drivers instead?
>> http://en.wikipedia.org/wiki/Space_fountain
>> The space fountain concept uses a closed circuit of iron pellets
>> travelling up and down through the tower to provide support. Most of
>> the tower can even be omitted above the atmosphere where the vacuum is
>> strong enough for the pellets to travel without significant friction,
>> the elevator cars coupling directly to the pellet stream for lift.
>
>Same crap, different pile.
Well, no. A space fountain doesn't have to contain anything
pressurized, it recycles all of its reaction mass, and it uses
electromagnetism instead of chemical reactions to provide thrust
against its structure. Most of the energy can be recycled, limited by
the efficiency of conversion to electricity and back. Those are some
pretty significant differences. Do you have specific critiques?
Ross A. Finlayson
failure mode where the pump goes offline, it falls over. Any talk
about a 100 kilometer tall freestanding structure, for example space
elevator or space fountain, with current and visible near-term
technology, is ridiculous.
I think the EGLTS systems, electromagnetic gun launch to space, offer
the most opportunity for SCRATS, safe cheap reliable access to space.
By cheap, I mean hundreds of times cheaper than any rocket could ever
be, reliable, more reliable than any rocket could ever be, and safe,
safer than any rocket could ever be.
With EGLTS, you mothball it, then ten years later, flip the switches
and its on-line, particularly where it has its own power supply. There
ain't no mechanisms to salvage the junked space elevator.
I think a good EGLTS system could be designed to be essentially
fail-safe, the magnets are preenergized and if they're not ready to
completely launch the pod then it doesn't go, otherwise, it goes all
the way out. (Problems with that include back EMF and pulsed power
switching.) Properly designed and operated, about the worst thing that
happens is the pod falls short, in all likelihood landing in the ocean.
The electromagnetic linear induction motor was invented around a
hundred years ago. Within five or so years, it was envisioned as a
method to launch things from Earth into space. That's a good idea, and
still holds true today. Initially explored experimentally in the 50's
and 60's during the space race, and coolly in the 70's by academic
space enthusiasts with 1000's of G's by undergraduates for 1's of
thousands of dollars, in the 80's as part of the raft of Strategic
Defense Initiative or Star Wars pie-tin in the sky brainstorming with
hard numbers, and over the past ten or more years as applied
technology, electromagnetic launch or EML has incrementally, if not
always expandingly, advanced in theory and applications.
The notion that the payload is essentially an abstract paperweight, and
that all of the launch apparatus is firmly emplaced on the ground,
constructed and maintained on the ground, accessible to technicians at
all stages of operation on the ground, in all weather on the ground,
not worthless after use on the ground, with negligeable threat of space
debris on the ground, solves lots of problems, because there ain't no
Jiffy Lube or AAA in space. The ETSMD technicians can wear Panama hats
and meander around the well-groomed ETSMD facility in electric carts.
Today, and in the future, rockets are used to launch things to space.
That's a fact, it's a given and accepted, it's true. There are
deficiencies in the use of rockets. Because of Newton's laws of
physics, which for terms of this discussion are assumed to hold, i.e.,
no simple anti-gravity or gravity-nullification devices, because of the
conservation of momentum the rocket is mostly expelled reaction mass
and almost totally one-use-only, basically like sending a 747 to the
smelter after its maiden flight. The ETSMD, Earth to Space Mass
Driver, obviates a lot of that waste.
I think EGLTS, electromagnetic gun launch to space, is, in realistic
terms, and don't look to me because I'm not necessarily a realist, nor
a mechanical engineer, EGLTS is in realistic terms _the_ next direction
of space launch technologies. Rockets improve and continue to improve,
but there won't be anything better until there's EGLTS, whether that's
five years from now, five hundred, or never.
Regards,
Ross F.
David Wilkinson
No. This whole thread is pure fantasy, about as practical as a chocolate
screwdriver. Get real, you proposers!
Bryan Derksen
<r...@tiki-lounge.com> wrote:
>The space fountain is pretty much a ludicrous idea. Consider the
>failure mode where the pump goes offline, it falls over. Any talk
>about a 100 kilometer tall freestanding structure, for example space
>elevator or space fountain, with current and visible near-term
>technology, is ridiculous.
That failure mode was discussed in the article I linked to. It's not
as catastrophic as you appear to believe, there wouldn't have to be
just one "pump" for starters.
Bryan Derksen
<da...@wilkinson6337.freeserve.co.uk> wrote:
>Bryan Derksen wrote:
>>Do you have specific critiques?
>
>No. This whole thread is pure fantasy, about as practical as a chocolate
>screwdriver. Get real, you proposers!
Well, that argument seems quite convincing to me. Never mind. :)
bz
$Z14....@news.indigo.ie:
I know a little chemistry and I tend to agree with you.
There is another 'minor problem'; the pi orbitals from the electons on
'benzine-like-rings' are strong and large.
I doubt that there is enough 'room' to interlink benzine like rings (six
member rings of sp2 hybredized carbons) and form a chain.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
bz
Pellets going up have to overcome earths gravity as well as supply lift for
the tower. They will have to start out very fast to supply that energy.
Then instead of letting them free fall back, they make the mistake of
accelerating them downward (of course that provides some lift to the tower
sections).
The tower is going to have to be covered with photocells to get energy, you
can't get all the energy from the pellets.
Have you ever seen what happens to punch cards in a card sorter when a card
jams? Imagine what happens when a pellet jams somewhere and millions of
other pellets pack in behind it and all release their kinetic energy at one
time, in one place.
David Wilkinson
then they ought to turn it into a TV comedy series. It could be funnier
than "Red Dwarf". No wonder the wikipedia is free! No one would pay to
read such stuff.
Where is Uncle Al with a few pithy comments on the whole misconception?
Jan Panteltje
<da...@wilkinson6337.freeserve.co.uk> wrote in
<d2roh5$g8o$1...@news6.svr.pol.co.uk>:
>
>Where is Uncle Al with a few pithy comments on the whole misconception?
louis_armstrong: what_a_wonderful_world
;-)
Dwayne
All these space towers are crap. Can we say high winds, & earthquakes. Plus
they are impossible to build. Don't think so? What the tallestest skycraper?
It's nowhere near as tall as the IDEA's being developed here. Look at the
new one being proposed in Hong Kong. The only reason it is going to be tall
is because it's cone shaped. So the wind load that's trying to blow the top
of the building over is incrementally reduced. Plus they haven't figured
out how to build it since no one country can supply enough steel or
concrete. Currently they are trying to figure out how to build it without
forcing increases in building material costs. AND this building is nowhere
near the IDEA's being proposed. Get real.
Dwayne
George William Herbert
>All these space towers are crap. Can we say high winds, & earthquakes.
We can say high winds and earthquakes. We can also apply engineering
and physics knowledge and numbers to the problem.
>Plus
>they are impossible to build. Don't think so? What the tallestest skycraper?
>It's nowhere near as tall as the IDEA's being developed here. Look at the
>new one being proposed in Hong Kong. The only reason it is going to be tall
>is because it's cone shaped. So the wind load that's trying to blow the top
>of the building over is incrementally reduced.
Please apply engineering and physics knowledge, using numbers.
>Plus they haven't figured
>out how to build it since no one country can supply enough steel or
>concrete. Currently they are trying to figure out how to build it without
>forcing increases in building material costs.
Many "one country"s can supply enough steel and concrete.
World production of steel is over a billion tons per year,
and China alone produced 25% of it in 2004. That's 250
million tons of steel, 30 million cubic meters. That would
be enough to make 3 towers 100 x 100 x 1000 meters high
out of solid steel or 100 with a 3% volumetric usage of
steel, a more accurate back of the envelope estimate
for real modern buildings. In just *China's* production.
The total world production of cement is about 2 billion tons.
Concrete is made up of 89% other materials, or 9 times more
total mass than just the cement going in. That works out
to a total of around 18 billion tons of concrete.
Or 7 billion cubic meters. Enough for 700 solid
concrete monoliths 100x100x1000 meters.
Please research the actual scope and scale of modern
industrial capacity worldwide.
> AND this building is nowhere
>near the IDEA's being proposed. Get real.
There is a difference between not cost effective and
not feasible, and between not feasible and not possible.
Physics and engineering tell us that very tall stayed
towers are possible. They may even be feasible and
within the scope of what could be manufactured by
a large industrial nation. The critics like you
who don't even show any sign of applying science,
engineering, or math to the analysis are simply
naive and misguided. The question is hard, but not
ridiculous to consider and analyze.
Whether there is any hope of them being cost effective
for any application is certainly open to debate.
Space elevators, a pure tension structure, are a whole
different issue. If we can make carbon nanotube filaments
long enough and bond them into a mechanically useful
ribbon or rope, the material has sufficient specific
strength to use reasonable taper ratios to Geosynchronous
Orbit. The mass required is quite manageable for small
payloads, the other problems are being worked right now,
and the cost estimates are no more than other major
aerospace projects today.
-george william herbert
gher...@retro.com
Bryan Derksen
<bz...@ch100-5.chem.lsu.edu> wrote:
>Pellets going up have to overcome earths gravity as well as supply lift for
>the tower. They will have to start out very fast to supply that energy.
Yes. They're accelerated to high speed by a maglev track on the
ground.
>Then instead of letting them free fall back, they make the mistake of
>accelerating them downward (of course that provides some lift to the tower
>sections).
>
>The tower is going to have to be covered with photocells to get energy, you
>can't get all the energy from the pellets.
Why not? The pellets travelling upward through a tower segment are
used to generate electricity, slowing them slightly, and that
electricity is used to accelerate the stream travelling downward.
There's some loss due to inefficiencies so the downward stream doesn't
reach the ground with quite the same speed as the upward stream, but
that can be made up for by power stations on the ground feeding into
the track where the pellets are turned around to go back up again.
>Have you ever seen what happens to punch cards in a card sorter when a card
>jams? Imagine what happens when a pellet jams somewhere and millions of
>other pellets pack in behind it and all release their kinetic energy at one
>time, in one place.
A misdirected pellet would make a mess if it hit the edge of an
accelerator, yes. One approach to making this survivable that comes to
mind is to give the accelerator arrays the ability to shunt pellets
across to the other pellet streams, to minimize the number of pellets
that would pass through a damaged accelerator while it's offline.
Alternately, perhaps one could use explosive bolts to jettison the
damaged accelerator immediately so that the stream can pass on through
to the next one unimpeded. One would probably need the ability to
remove accelerators from an active stream anyway, for routine
maintenance.
No system's perfect, I'm just pointing out this one as a more
plausible approach to an actively-supported high-altitude tower than
the original poster's rocket-pipe.
Dwayne
"George William Herbert" <gher...@retro.com> wrote in message
news:1153jc4...@corp.supernews.com...
> Dwayne <ddc...@yahoo.ca> wrote:
>>All these space towers are crap. Can we say high winds, & earthquakes.
>
> We can say high winds and earthquakes. We can also apply engineering
> and physics knowledge and numbers to the problem.
>
>>Plus
>>they are impossible to build. Don't think so? What the tallestest
>>skycraper?
>>It's nowhere near as tall as the IDEA's being developed here. Look at the
>>new one being proposed in Hong Kong. The only reason it is going to be
>>tall
>>is because it's cone shaped. So the wind load that's trying to blow the
>>top
>>of the building over is incrementally reduced.
>
> Please apply engineering and physics knowledge, using numbers.
The following analysis is acurate to 3 significant figures.
Low Earth Orbit = h = 100,000m
d = 0.25m (assumed internal radius of stupid pipe going into LEO)
A = pi*(d/4) = 0.05 m^2 (internal footprint of assumed pipe)
V = A*h = 5,000 m^3 (volume of water in assumed pipe)
p = 1000 kg/m^3 (density of water @ STP -101kPa & 25C)
m = p*V = 5,000,000 kg (mass of water)
g = 10kg*m/s^2 (Gravitational constant for planet Earth -> the planet we
live on for those that don't know)
Fg = m*g = 50,000,000 N (force, due to gravity, water exerts on bottom
surface of cylinder)
P = Fg/A = 1,000,000,000 N/m^2 = 1,000,000,000 Pa (pressure exerted on
bottom of cylinder, also required pressure to pump water to top).
P = 1,000,000,000 *14.5psi/101,300Pa = 143,000,000 psi
Good luck. And yes buddy I can do math. Can you?
> There is a difference between not cost effective and
> not feasible, and between not feasible and not possible.
The sentence "The project is not feasible because it's not cost effective"
is one I have heard many times.
Dwayne
Robert Clark
largely incompressible and it's easier to get an idea of the pressures
involved. Quite likely you would actually want to use gases since the
pressures required would be less.
For gases you can use the exponential reduction in pressure with
altitude. This is explained here:
HYDROSTATIC LAW - INTEGRATED FORM
http://www.owlnet.rice.edu/~phys443/handouts/hydro.html
and:
The isothermal atmosphere.
http://farside.ph.utexas.edu/teaching/sm1/lectures/node54.html
Note this is for the approximation of an atmospheric temperature that
is constant with height. For the real atmosphere this approximation
gets worse the higher you go up. But for a gas enclosed in a tube you
might be
able to get close to this if the gas moves fast enough so not to stay
in the tube too long. You might also be able to apply electrical
heating elements to the tube with a temperature gradient depending on
altitude.
The formula given in the second link above is pressure P =
P0*e^(-z/z0), with P0 the pressure at the surface, z the altitude in
kilometers. The quantity z0 is the scale height in kilometers and
equals RT/mg, with R the ideal gas constant, 8.31 joules/mole/degree, T
the constant temperature of the gas in Kelvin, m the molecular weight
of the gas and g the acceleration due to gravity, 9.81 m/s^2.
If you use hydrogen gas of molecular weight 2, then when T=300K, the
pressure will drop by the factor e^(100*2*9.81/8.31*300) = 2.2 at
100km. So if you want to have 6000 psi at the top you would start the
gas at 13,200 psi on the ground.
Other gases you might want to try would be helium at molecular weight
4, water as steam at molecular weight 18 and air at molecular weight
29.
You might want to use helium instead of hydrogen because it is
non-flammable, an important consideration for a 100km long pipeline.
But helium is much more expensive and not as abundant as hydrogen.
Air would be the obvious and the least expensive solution but you
would have to put it at high temperature T so that the pressure at the
bottom would not have to be too great. For example, using T = 2000K for
air at molecular weight 29, the pressure drops by
e^(100*2*9.81/8.31*2000) = 5.5 at 100km.
Steam becomes a good possibility when you consider the space shuttle
main engines produce steam as exhaust at 3000K temperature and 6000 psi
pressure. Then the pressure drops using SSME exhaust at 3000K by a
factor of e^(100*18*9.81/8.31*3000) = 2.03 at 100km.
These calculations as for the ones for liquid are intended to give an
idea of the pressures involved. What still needs to be included in the
calculations is the drop in pressure due to friction and viscosity for
a fluid traveling in a 100km long tube.
Robert Clark
Jonathan Barnes wrote:
> ----- Original Message -----
> From: "Robert Clark" <rgrego...@yahoo.com>
>
> > > > To confirm the 3700m/s speed at 100 km,
>
> ( inapplicable formula used gas in a pipe is not a solid body )
>
> > >
> > > Steam pipe practice.... MAX velocity 100 m / sec
> > >
> > > We are talking runs of pipe under 100m long
> > >
> > > Your going to need a pipe with several METERS thick steel walls
to
> > hold your
> > > pressures.
> > >
> > > Lets put things in perspective... take a 1/2m diameter steam
pipe,
> > stainless
> > > steel, 50mm wall
> > >
> > > Weight per metre, 573 Kg, so that's 57,300 tons for a 100 Km
pipe.
> > >
> > > Lets have just a 100 meter run and hustle some steam down it....
7
> > bar inlet
> > > pressure.
> > >
> > > For a one bar ( 14.7 PSI ) pressure loss over the length, the
entry
> > speed
> > > would be 52 m/s
> > >
> >
> > The weight of the fluid and of the tube is being supported by the
high
> > pressure or high velocity fluid being directed aft from vents along
the
> > entire length of the tube.
> > As for the thickness of the tube, this page gives a commonly used
> > formula for calculating the thickness of pipe required to hold a
given
> > fluid pressure, called Barlow's formula:
> >
> > Barlow's Formula Calculator.
> > http://www.texaspipe.com/barlows_formula.html
> >
> > The formula is:
> >
> > P=2St/D, where P is the pressure in the pipe, S is the tensile
> > strength, t is the thickness, and D is the inner diameter of the
pipe.
> > So t = PD/2S.
> >
> > Then for carbon fiber with tensile strength of 1,000,000 psi and
with
> > a pressure in the tube of 100,000 psi, a 1 cm thick tube would
suffice
> > for a tube with an inner diameter of 20 cm.
> > Keep in mind though that the pressure would likely be less than
this
> > if we used the less dense gases rather than liquids for the fluid.
> >
> >
> > Bob Clark
> >
>
> Carbon fibre and carbon fibre laminate are different...
> A binder is needed to hold the fibre. ( and stopping the gas leaking
:-) )
>
> Your pipe formula is for non directional materials. carbon laminates
would
> be directional.
>
> 100,000 PSI.... = 6,800 bar, air density at STP 1.2 Kg /m^3...
hydrogen
> density 0.042 ( is H monatomic ? )
>
> Hydrogen at 6,800 bar, density 280 kg /m^2 ( twice this if diatomic
)
> 100 Km high column static pressure = 2750 bar.
>
> material.
>
> Ignoring the vaporisation of the pipe :-)
> Assume a loss of ( 6800 - 2750 ) / 1000 = 4 bar / 100 m a speed of
120 m/s
> is closer to your gas speed.
>
> Loss should rise with the square of velocity, so a loss of 53000 psi
per
> 100m at 3600 m/s would be expected...
> of course the formulas would be way outside their valid zones, and
would
> under estimate the loss.
>
> GET REAL
>
> You are orders of magnitude away from the possible.
>
> Jonathan
>
> Barnes's theorem; for every foolproof device
> there is a fool greater than the proof.
>
> To reply remove AT
According to Dani Eder who definitely would know, carbon fiber is
already being wound into solid rocket motor casings:
Carbon fiber (Dani Eder)
http://yarchive.net/space/exotic/carbon_fiber.html
To have the strength both vertically and horizontally, wind it in both
directions.
To resist the temperatures one possibility is to coat the interior
with tantalum hafnium carbide:
tantalum hafnium carbide.
"The alloy tantalum hafnium carbide (Ta4HfC5), with a melting point of
4,215 C (7,619 F), is one of the most refractory substances known."
http://www.britannica.com/nobel/micro/254_6.html
Where are you getting this calculation from:
"Assume a loss of ( 6800 - 2750 ) / 1000 = 4 bar / 100 m a speed of
120 m/s
is closer to your gas speed."
In any case using heated exhaust gases is only one of the proposals
for implementing the idea.
Bob Clark
Bryan Derksen
>The following analysis is acurate to 3 significant figures.
>Low Earth Orbit = h = 100,000m
>d = 0.25m (assumed internal radius of stupid pipe going into LEO)
>A = pi*(d/4) = 0.05 m^2 (internal footprint of assumed pipe)
>V = A*h = 5,000 m^3 (volume of water in assumed pipe)
Your analysis just lost all of its accuracy at this point because this
subthread hasn't been about the "rocket pipe" version of a space tower
for almost three days now. The space fountain has pipes containing
vacuum instead of fluid and the space elevator doesn't have any sort
of pipe at all, just a cable. Please try to analyze the designs that
are actually being discussed rather than just the design you most love
to hate.
Robert Clark
At the beginning of this thread the pressure of water was calculated
to be ca. 100,000 psi, for which pumps and the required high strength
materials already exist. Check that calculation again.
Bob Clark
Pete Lynn
"Dwayne" <ddc...@yahoo.ca> wrote in message
news:Jan4e.900949$6l.448110@pd7tw2no...
"The following analysis is accurate to 3 significant figures."
"g = 10 ms^-2 Gravitational constant for planet Earth"
Very amusing - I especially liked the gravitational *constant* part -
apparently independent of altitude.
This topic came up a few years ago. Geoffrey Landis wrote a paper in
this area. - "High altitude launch for a practical SSTO" I have it in
PDF. I would expect GWH to have far more besides.
For a 15 km tower at 2000 ton payload, cast steel 5300 ton, (taper ratio
2.6), graphite epoxy 280 ton, (no taper required).
I can not recall the costs, (ssp archives?), but I think the steel tower
might have been in the $10 million range, depending on erection costs,
(pressure suits). The material costs are in the $1 million range.
A previous analysis of his concluded that towers up to 2250 km might be
possible with advanced materials. This sounds right to me.
BOTE calculations should roughly verify all of this for you.
Other results were:
5 km 31.2% payload increase
10 km 60.2%
15 km 84%
20 km 104.9%
25 km 122.5%
I think these were based on the effects of aerodynamic drag reduction
and ISP improvements mainly. This does not account for the significant
design simplification/weight advantages, (no aero shell), etcetera. The
easing of margins would also have a significant effect on cost.
Pete.
Jonathan Barnes
Jonathan Barnes wrote:
> Where are you getting this calculation from ?
>>"Assume a loss of ( 6800 - 2750 ) / 1000 = 4 bar / 100 m a speed of
>>120 m/s is closer to your gas speed."
I'm " streaching " the graphs I use for the pressure drops in steam pipes,
with a little jigery pokery to translate from kg/hr to m/s useing density
and cross sectional area.
The graphs come from Spirax Saroc and might be available through their web
sight www.SpiraxSarco.com
I should be within an order of magnitude, which is more than accurate enough
for this thread :-)
--
Dwayne
"Pete Lynn" <pe...@peterlynnkites.com> wrote in message
news:xZp4e.537$5F3...@news-server.bigpond.net.au...
The radius of the Earth is 6378km, so 100km is negligible. I used 3 sig figs
in the calculation. Please learn the scientific approach before critisizing
my work.
Dwayne
Jim Logajan
> The following analysis is acurate to 3 significant figures.
If that were true, you'd use g = 9.81, not g = 10. Your analysis and
round numbers all suggest a computation to 1 significant figure - with
odd exceptions.
In this context the problem only calls for 1 significant figure ("sf")
values - or even just an order of magnitude estimate.
> Low Earth Orbit = h = 100,000m
> d = 0.25m (assumed internal radius of stupid pipe going into LEO)
> A = pi*(d/4) = 0.05 m^2 (internal footprint of assumed pipe)
Your equation for area appears wrong (typo?). It should be:
A = pi*d*d/4
Yet you gave the correct value, but only to 1 sf. Using 2 sfs would set A
= 0.049. Three sfs gives 0.0491.
> V = A*h = 5,000 m^3 (volume of water in assumed pipe)
> p = 1000 kg/m^3 (density of water @ STP -101kPa & 25C)
> m = p*V = 5,000,000 kg (mass of water)
> g = 10kg*m/s^2 (Gravitational constant for planet Earth -> the planet
> we live on for those that don't know)
The value 'g' is often called the "standard gravity". The "gravitational
constant" is a different value with different units, although
"gravitational constant for planet Earth" may or may not remove the
ambiguity.
> Fg = m*g = 50,000,000 N (force, due to gravity, water exerts on bottom
> surface of cylinder)
> P = Fg/A = 1,000,000,000 N/m^2 = 1,000,000,000 Pa (pressure exerted on
> bottom of cylinder, also required pressure to pump water to top).
> P = 1,000,000,000 *14.5psi/101,300Pa = 143,000,000 psi
Your standard atmosphere in PSI, 14.5, is 3 sf (though the value is
normally quoted as 14.7). Yet 101,300 is 4 sf. Not a consistent usage of
significant figures.
Also, a little algebra would have shown that the cross sectional area is
irrelevant when computing the pressure:
P = m*g/A
= p*V*g/A
= p*A*h*g/A
= p*h*g
Pete Lynn
> >
> > "The following analysis is accurate to 3 significant
> > figures."
> > "g = 10 ms^-2 Gravitational constant for planet Earth"
> >
> > Very amusing - I especially liked the gravitational
> > *constant* part - apparently independent of altitude.
>
> The radius of the Earth is 6378km, so 100km is
> negligible. I used 3 sig figs in the calculation. Please learn
> the scientific approach before critisizing my work.
I may be wrong, however:
0 km g = 9.81 ms^-2 (3sf)
100 km g = 9.51 ms^-2 (3sf)
So within three significant figures, it is neither "accurate" or
"negligible", hence my amusement.
I am reminded of a quote by Oscar Wilde - teenager?
Pete.