Rockets not carrying fuel.

Uncle Al wrote in message ...
Robert Clark wrote:

What would be the fuel requirements for a rocket that did not carry
its own fuel? Say a rocket with the payload capacity of the shuttle
and with engines of the efficiency of the shuttle main engines?

Why don't you beam a laser at it to blast the air underneath into
plasma and push the thing up? That was deeply supported by NASA
despite the obvious square-cube contradiction.

A problem with the Leik Myrabo "light craft" is that the lasers have
to be very powerful to maintain the concentrated energy at the
distance of the spacecraft and to overcome dispersion by the
atmosphere.
If large scale carbon nanotubes do become available it might work to
form a 100km long electrical power cable to power a laser carried on
board the ship. Then that would eliminate the atmospheric dispersion
and attenuation problems.

Riding Laser Beams to Space
By Leonard David
Senior Space Writer
posted: 06:58 am ET
05 July 2000
http://www.space.com/businesstechnol...on_000705.html


Bob Clark

In sci.physics,

wrote
on Thu, 31 Jul 2003 18:32:50 GMT
:
In article , The Ghost In The Machine writes:
In sci.physics,

wrote
on Wed, 30 Jul 2003 18:15:28 GMT
:
In article , (Gregory L. Hansen) writes:
In article ,
wrote:
In article ,
(Gregory L. Hansen) writes:
In article ,
Robert Clark wrote:
From this web page, the weight of the shuttle external tank with the
liquid oxygen and hydrogen is 1.6 million pounds:

EXTERNAL TANK
http://science.ksc.nasa.gov/shuttle/...ewsref/et.html

But the amount of liquid oxygen that is burned is only 2,787 pounds
per second and the amount of hydrogen 465 pounds per second.

Nanotube productions methods are advancing quickly. Suppose it is
possible to make a fuel line of carbon nanotube material hundreds of
kilometers long. Could fuel be pumped up to a rocket accelerating to
orbital velocity?
What would be the fuel requirements for a rocket that did not carry
its own fuel? Say a rocket with the payload capacity of the shuttle
and with engines of the efficiency of the shuttle main engines?



Bob Clark

Practical considerations aside, I think it's a neat idea.

Practical considerations aside, I think that teleportation is a neater
idea:-)

Nah... the hose to the gas tank has sort of a Jules Verne quality to it.
It's cute, it's quaint. It has sort of the same quality as a torpedo
powered by an internal combustion engine.

:-))

This thread is beginning to remind me of the movie "Wild Wild West"
for some reason... :-) (The 1999 variant with Will Smith.)

You mean in the sense of being divorced from reality?:-)

Well, yeah. :-)


But yeah, one could use an ICE for a torpedo; just remember to
fill that oxygen tank, too.... :-)

Sure.

No one said it had to be the most efficient. :-) Then again,
I'd have to look; presumably there are more efficient
propulsion plants for torpedoes than an ICE with supplied oxidizer.


Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"


--
#191,
It's still legal to go .sigless.

In article , The Ghost In The Machine writes:
In sci.physics,

wrote
on Thu, 31 Jul 2003 18:32:50 GMT
:
In article , The Ghost In The Machine writes:
In sci.physics,

wrote
on Wed, 30 Jul 2003 18:15:28 GMT
:
In article , (Gregory L. Hansen) writes:
In article ,
wrote:
In article ,
(Gregory L. Hansen) writes:
In article ,
Robert Clark wrote:
From this web page, the weight of the shuttle external tank with the
liquid oxygen and hydrogen is 1.6 million pounds:

EXTERNAL TANK
http://science.ksc.nasa.gov/shuttle/...ewsref/et.html

But the amount of liquid oxygen that is burned is only 2,787 pounds
per second and the amount of hydrogen 465 pounds per second.

Nanotube productions methods are advancing quickly. Suppose it is
possible to make a fuel line of carbon nanotube material hundreds of
kilometers long. Could fuel be pumped up to a rocket accelerating to
orbital velocity?
What would be the fuel requirements for a rocket that did not carry
its own fuel? Say a rocket with the payload capacity of the shuttle
and with engines of the efficiency of the shuttle main engines?



Bob Clark

Practical considerations aside, I think it's a neat idea.

Practical considerations aside, I think that teleportation is a neater
idea:-)

Nah... the hose to the gas tank has sort of a Jules Verne quality to it.
It's cute, it's quaint. It has sort of the same quality as a torpedo
powered by an internal combustion engine.

:-))

This thread is beginning to remind me of the movie "Wild Wild West"
for some reason... :-) (The 1999 variant with Will Smith.)

You mean in the sense of being divorced from reality?:-)

Well, yeah. :-)


But yeah, one could use an ICE for a torpedo; just remember to
fill that oxygen tank, too.... :-)

Sure.

No one said it had to be the most efficient. :-) Then again,
I'd have to look; presumably there are more efficient
propulsion plants for torpedoes than an ICE with supplied oxidizer.





I'm sure many things were tried. Remember, there are two
considerations involved.

1) The required engine lifetime is quite short.
2) On the other hand, the fuel should remain stable under long
storage conditions.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

In article ,
The Ghost In The Machine wrote:
In sci.physics,


But yeah, one could use an ICE for a torpedo; just remember to
fill that oxygen tank, too.... :-)

Sure.

No one said it had to be the most efficient. :-) Then again,
I'd have to look; presumably there are more efficient
propulsion plants for torpedoes than an ICE with supplied oxidizer.

Earlier torpedoes used compressed gasses, air or CO2, in piston engines.
At least one used a flywheel. And batteries were and are used. But you
get a lot of kick from an internal combustion engine, a lot more than from
an equivalent amount of compressed air.

--
"A good plan executed right now is far better than a perfect plan
executed next week."
-Gen. George S. Patton

Uncle Al wrote in message ...
Dan Tilque wrote:

Robert Clark wrote:


But the amount of liquid oxygen that is burned is only 2,787
pounds per second and the amount of hydrogen 465 pounds per
second.

Those numbers don't look right. Shouldn't the LOX be about 8

A boundary layer of raw fuel is pumped down the inner walls of each
combustion chamber to cool the walls. If you look at an apolitical
rocket system launching - the Saturn moon rockets - you note closeup
of the running engines at launch shows a black collar around each
exhaust that flashes white hot a bit later on down. The black is a
sheath of pyrolyzing kerosene that finally combusts.

Nanotube productions methods are advancing quickly. Suppose
it is possible to make a fuel line of carbon nanotube material
hundreds of kilometers long. Could fuel be pumped up to a
rocket accelerating to orbital velocity?

Got to give you credit for thinking outside the box. This
certainly is a unique idea.

But I can't imagine there exists a pump that could do this. Or
even come close. Especially since it has to operate at liquid
oxygen temps.

Turbopumping is no big deal, the Germans had it down pat for the V-2.
Pumping anything at sonic velocities through a long thin pipe is
really stooopid. You plug in the appropriate dimensionless number for
flow, you see where the turbulent flow regime begins, then you
carefully plan the project so you retire before the first shakedown
demo.

What insulates the cryogen from ambient temp? Nothing. Stooopid
idea.

Well if you really think this idea is stupid, then you should read up
on space elevators, rotavators, and magic bean stalks. Because
"stupid" people like A. C. Clark, Hans Moravec, Austronatov?, and
Konstantine T. have been theorizing about them for decades.

In article ,
Tony Rusi wrote:
Uncle Al wrote in message
...
Dan Tilque wrote:

Robert Clark wrote:


But the amount of liquid oxygen that is burned is only 2,787
pounds per second and the amount of hydrogen 465 pounds per
second.

Those numbers don't look right. Shouldn't the LOX be about 8

A boundary layer of raw fuel is pumped down the inner walls of each
combustion chamber to cool the walls. If you look at an apolitical
rocket system launching - the Saturn moon rockets - you note closeup
of the running engines at launch shows a black collar around each
exhaust that flashes white hot a bit later on down. The black is a
sheath of pyrolyzing kerosene that finally combusts.

Nanotube productions methods are advancing quickly. Suppose
it is possible to make a fuel line of carbon nanotube material
hundreds of kilometers long. Could fuel be pumped up to a
rocket accelerating to orbital velocity?

Got to give you credit for thinking outside the box. This
certainly is a unique idea.

But I can't imagine there exists a pump that could do this. Or
even come close. Especially since it has to operate at liquid
oxygen temps.

Turbopumping is no big deal, the Germans had it down pat for the V-2.
Pumping anything at sonic velocities through a long thin pipe is
really stooopid. You plug in the appropriate dimensionless number for
flow, you see where the turbulent flow regime begins, then you
carefully plan the project so you retire before the first shakedown
demo.

What insulates the cryogen from ambient temp? Nothing. Stooopid
idea.

Well if you really think this idea is stupid, then you should read up
on space elevators, rotavators, and magic bean stalks. Because
"stupid" people like A. C. Clark, Hans Moravec, Austronatov?, and
Konstantine T. have been theorizing about them for decades.


My favorite is an electromagnetic cannon shooting metal slugs into the
bottom of an elevator that catches the slugs and shoots them back down to
a receiving station. I wonder if the birds would know to stay out of the
way.


--
"A good plan executed right now is far better than a perfect plan
executed next week."
-Gen. George S. Patton

(Robert Clark) wrote:
From this web page, the weight of the shuttle external tank with the
liquid oxygen and hydrogen is 1.6 million pounds:

EXTERNAL TANK
http://science.ksc.nasa.gov/shuttle/...ewsref/et.html

But the amount of liquid oxygen that is burned is only 2,787 pounds
per second and the amount of hydrogen 465 pounds per second.

Nanotube productions methods are advancing quickly. Suppose it is
possible to make a fuel line of carbon nanotube material hundreds of
kilometers long. Could fuel be pumped up to a rocket accelerating to
orbital velocity?
What would be the fuel requirements for a rocket that did not carry
its own fuel? Say a rocket with the payload capacity of the shuttle
and with engines of the efficiency of the shuttle main engines?

In addition to the problems others have mentioned, if you somehow
did manage to pump fuel up to the shuttle fast enough through a hose of
manageable size (assuming that you could keep the hose from getting burned
up by the exhaust and air friction), pretty soon you will get to the point
at which the kinetic energy of the fuel exceeds any chemical energy it could
possibly have (same reason as why you need to carry so much chemical fuel for
each little bit of payload in the first place). At this point, you might as
well select what you send up the hose for optimum pumping characteristics and
never mind about its fuel characteristics, because at this point the shuttle
has become an Orbital Water Wiggle(tm).

--
Lucius Chiaraviglio
Approximate E-mail address:
To get the exact address: ^^^ ^replace this with 'r'
|||
replace this with single digit meaning the same thing
(Spambots of Doom, take that!).

jimmydevice wrote:

Robert Clark wrote:
snipped?
The ratio of liquified hydrogen to gas is 880 to 1, if you calculate
the fuel requirement, you will need over 1 million atm to fuel the
engines.
# Density, Liquid @ B.P., 1 atm: 4.23 lb./cu.ft.
# Density, Gas @ 68°F (20°C), 1 atm: 0.005229 lb./cu.ft.
Jim Davis

Forgot this little fact
# Critical Pressu 188 psia (12.9 atm)
so you have liquid again.
Jim Davis

(Henry Spencer) wrote in message ...
In article ,
Robert Clark wrote:
The most common measure of rocket engine efficiency given is ISP,
thrust to fuel burn rate. Another common measure given is oxidizer to
fuel ratio.
What I need is a like a combination of these (it can be calculated
from them): thrust to (fuel + oxidizer) burn rate...

It's called specific impulse, aka Isp.

Note that "fuel" is an imprecise term; it is sometimes used as a synonym
for "propellant", meaning both fuel and oxidizer (and anything else
needed, e.g. a separate turbine-drive propellant in the Soyuz launcher).
Isp for rockets counts all propellants, not just one of them.


Thanks for the response. I was confused by the fact that ISP's for
ramjets were given in the thousands. This is because they don't
include the amount of oxygen that must be used to support combustion.
Simply using the word "fuel" in the definition of ISP led me to
believe that was the case as well for rockets.
But it makes sense that they wouldn't include the oxygen for ramjets
since that doesn't have to be carried along. For rockets it makes
sense to include the oxygen or oxidizer since that has to be carried
along with the actual combustible fuel.



Bob Clark