Rockets not carrying fuel.

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

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
times the LH?


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.

--
Dan Tilque

On Mon, 28 Jul 2003 22:41:16 -0700, in a place far, far away, "Dan
Tilque" made the phosphor on my monitor glow in
such a way as to indicate that:

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
times the LH?

Yes, if the propellant were burned stoichiometrically. But for
reasons of propulsion efficiency, it's not.

6:1 turns out to be about the best mixture ratio, because the value of
more low-mass molecules (hydrogen) turns out to provide a higher
specific impulse than getting the maximum energy from the reaction.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

"Robert Clark" wrote in message
om...
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?

I believe it's only possible to pump fluids to a certain height - after
which you just cant push any more

Doug

"Doug Ellison" wrote ...

I believe it's only possible to pump fluids to a certain height - after
which you just cant push any more

*ahem* After a certain height you can't _pull_ anymore.
I don't think there is a limit to how far you can _push_ liquids up.

However the prospect of the immense pressures involved might
give some people pause - in which case you can always have
'staging posts' along the way.

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?

Intensely stooopid idea. The rocket still lifts most of the fuel,
plus the pipe, plus the ice on the pipe. Friction with the piping
wall prevents flow. Expel your breath, then expel it through a soda
straw. Compare flow rates

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.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

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.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

(Robert Clark) wrote in message . com...
[snip]
Nanotube productions methods are advancing quickly. Suppose it is
possible to make a fuel line of carbon nanotube material hundreds of
kilometers long.

Listen. If you could build a tube that could carry the fuel, why
would you need the shuttle? Why not just climb up the tube?

Could fuel be pumped up to a rocket accelerating to
orbital velocity?

Nope! If you are going to push the fuel into the shuttle at
the speed the shuttle is moving, you've got still the same
energy requirements. You've moved them onto the tube, but
you still have to push the fuel just as hard. So, effectively,
you are climbing up the tube. Once again, what use is the
shuttle in this scenario? Why not just climb up the tube?
Socks

"Doug Ellison" wrote in message
...

"Robert Clark" wrote in message
om...
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?

I believe it's only possible to pump fluids to a certain height - after
which you just cant push any more

You can always push, but there is a limit to how high you can pull.

In article ,
Rand Simberg wrote:
Those numbers don't look right. Shouldn't the LOX be about 8
times the LH?

Yes, if the propellant were burned stoichiometrically. But for
reasons of propulsion efficiency, it's not.
6:1 turns out to be about the best mixture ratio, because the value of
more low-mass molecules (hydrogen) turns out to provide a higher
specific impulse than getting the maximum energy from the reaction.

In fact, it's a bit more complicated than that. Hydrogen improves the
exhaust properties so much, at so little cost in mass, that about 4:1
would yield the highest specific impulse.

But hydrogen is so bulky that you would pay a significant price for this,
first at the engine level and then at the vehicle level. At the engine
level, the hardware gets bigger and the required pump power goes up a lot
(pumps pump volume, not mass). At the vehicle level, the huge tanks are a
problem in several ways, not least being mass.

So the bottom line is that while you get maximum specific impulse at 4:1,
this costs you so much in extra hardware mass that it's not worth it --
you get maximum *vehicle* performance at leaner mixture ratios. Some
early hydrogen stages, designed before hydrogen's problems were well
understood, ran at 5:1, but modern belief is that 6:1 is about optimal.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |