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National Aerospace Plane (X-30) announced 20 years ago



 
 
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  #11  
Old February 13th 06, 01:39 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

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tomcat wrote:
[...]
Wings use air to gain an advantage on gravity. Therefore, they can
reach the airless void using less energy than a vertical tublular
rocket.


That last statement is debatable.

When you want to reach orbit, height isn't important, and speed is. Since
speeds approaching orbital velocities are deeply unhealthy in an
atmosphere, you're going to want to do the bulk of your acceleration when
you're above it. The usual flight profile of a launching spacecraft is to
go vertically up through the bulk of the atmosphere, and then rotate
sideways and accelerate sideways once it's above it. All wings will do here
is to add on weight and drag, which will eat into your payload.

[...]
The proof that wings gain an advantage is that a bomber can reach
20,000 feet and stay there for the hours it takes to reach target and
return on 1/10th of the thrust to weight ratio that a vertical tubular
rocket requires just to slowly leave the launch pad.


Sure, but that bomber isn't in orbit. The fastest jet aircraft ever made was
the Lockheed SR-71, which managed to get to Mach 3.3. Orbital velocity is
about equivalent to Mach 25. I think you might be confusing being in orbit
with being high up.

There is some benefit for being high up when you launch a spacecraft; but
it's got nothing to do with speed. Instead it's all about being able to
avoid having to fly your very energy-expensive rocket through a thick
atmosphere and having to have to use rocket nozzles optimised for sea-level
air.

So, basically: on the way up, wings are a drag. (Literally.) They're heavy
and get in the way. On the way down, they're definitely useful, but there
are other approaches that are lighter and more effective, such as a
inflatable parasail: it's a fraction of the weight of a fixed wing, and
doesn't impose drag on launch. SSTOs are so marginal anyway that the cost
of adding a wing, with undercarriage, reinforced stress structure etc may
well put you completely out of business.

- --
+- David Given --McQ-+
| | "Never attribute to malice what can be adequately
| ) | explained by stupidity." --- Nick Diamos
+-
www.cowlark.com --+

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  #12  
Old February 14th 06, 05:32 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

"tomcat" wrote in message
oups.com...

Wings use air to gain an advantage on gravity. Therefore, they can
reach the airless void using less energy than a vertical tublular
rocket.


The goal isn't getting to orbit using the least energy -- it's
getting to orbit the cheapest, safest way. The energy expended
by a rocket is often inexpensive LOX and LH2. LOX is virtually
free and LH2 is a very low % of operating costs. I think you made
that point before; I'm not saying you disagree with it.

It makes no sense using a tremendously complicated,
very expensive hypersonic airbreathing winged vehicle to save a
few dollars of propellant.


The proof that wings gain an advantage is that a bomber can reach
20,000 feet and stay there for the hours it takes to reach target and
return on 1/10th of the thrust to weight ratio that a vertical tubular
rocket requires just to slowly leave the launch pad.


This only illustrates that jet engines have much better specific
fuel consumption than rockets. The B-52H TF33 jet engine
has a specific fuel consumption of about 0.56 lb fuel per
pound thrust per hr. The shuttle SSME consumes about 9.4
lb propellant per pound thrust per hr.

A rocket can produce lots of thrust, but its specific propellant
consumption is poor. It's better to let the rocket do what it does
best -- produce lots of thrust and get out of the atmosphere
quickly. Wings just slow you down.

If you replaced the B-52's jet engines with rockets, it couldn't
fly for hrs, despite having wings. It's not the wings that make
the big difference, it's the engine type.


In short, you have to get from here to orbit and the best method is a
winged or waverider vehicle.


The best way is the cheapest, most reliable way. Cheap means
a combination of operating costs and development costs.
Nobody gives you an award for getting to orbit the most
romantic way, or the coolest way.

The airfoil vehicle, however, is more
difficult to design than a vertical tubular rocket.


Boy, is that right.. A winged hypersonic airbreathing
orbital launcher is so difficult nobody has figured out how to
do it.


a waverider design shouldn't be all that difficult with
the knowledge and materials base that exists in 2006.


Add about a hundred years to that and you're closer to
correct.

And, slush hydrogen tanks have
solved the volume problem for hypergolic hydrogen/lox burners like the
SSME.

Hydrogen/LOX engines are NOT hypergolic.

-- Joe D.


  #13  
Old February 15th 06, 02:39 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

tomcat wrote:
Wings use air to gain an advantage on gravity. Therefore, they can
reach the airless void using less energy than a vertical tublular
rocket.


Not necessarily. A winged vehicle necessarily spends more time in the
atmosphere; and hence spends more fuel on atmospheric drag. In
addition, because it spends more time to reach orbit, the gravity
losses are higher; although they are offset by the higher efficiencies
of wings at supporting the vehicle. Finally, winged vehicles are much
less efficient on the final orbital insertion burn; the dry mass is
very significantly increased by the presence of wings- this makes the
final insertion burn require multiple times more fuel.

Unless you are using an airbreathing engine it's all at best a wash or
only very modest improvements indeed.

They also enable a spacecraft to 'fly' to a runway and land
softly after deorbit.


Yes, although landing speeds can be very high.

The proof that wings gain an advantage is that a bomber can reach
20,000 feet and stay there for the hours it takes to reach target and
return on 1/10th of the thrust to weight ratio that a vertical tubular
rocket requires just to slowly leave the launch pad.


Yes, although that is more to do with high ISP of airbreathing engines
and the high lift/drag ratio that is achievable only at low speeds.

Today, however, a waverider design shouldn't be all that difficult with
the knowledge and materials base that exists in 2006. Titanium is
plentiful and easily worked. The SSME (Space Shuttle Main Engine) has
proven to be reliable. The tile problem has been solved (Don't tell
NASA -- they haven't found out yet.). And, slush hydrogen tanks have
solved the volume problem for hypergolic hydrogen/lox burners like the
SSME.


All those things were known about when the Shuttle was built. It's not
that simple.

tomcat


  #14  
Old February 26th 06, 12:59 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

Ian Woollard wrote:
tomcat wrote:
Wings use air to gain an advantage on gravity. Therefore, they can
reach the airless void using less energy than a vertical tublular
rocket.


Not necessarily. A winged vehicle necessarily spends more time in the
atmosphere; and hence spends more fuel on atmospheric drag.


Not necessarily: NASA Helios Prototype flew to 96,863 feet in 2001
using propellers shovelling air powered by 28 horsepower motors fueled
by sunlight from solar cells on it's wings. Helios was designed as
proof of concept for "atmospheric satellites" intended to stay aloft
for weeks, or months at a time, refuling daily from solar power above
the clouds.

The issue with wings is wingloading. Helios had 13 ounces loading per
square foot of wing. The Piper Cub has 6.7 pounds. The Concorde had 12
pounds.

You don't mind thinking big about fuel expendatures and thinking big
about money expendatures -- try thinking BIG about wings.

The SKYLON is being designed to mine oxidizer from the atmosphere.
http://en.wikipedia.org/wiki/Skylon
http://www.reactionengines.co.uk/main.php?content=index

Up to 5.5 mach it is airbreathing. The ratio of H2 to O2 is 1:8 by
weight. 8/9ths of the weight of the fuel mixture is not airlifted until
the air is very much thinner than sea level. THEN, getting up to speed
the O2 is brought onboard, AFTER the air density is far less than one
tenth as thick. Skylon has stubby little wings, which is why its
projected payload is so low.

Try thinking 20 pounds or less per square feet of wing and you come up
with a biplane that looks more like the Concorde riding piggyback on
the B2-Spirit (with 8,000+ square feet of wings).

In
addition, because it spends more time to reach orbit, the gravity
losses are higher; although they are offset by the higher efficiencies
of wings at supporting the vehicle.


There is no such thing as "gravity losses" as long as a vehicle is
ascending. Gravity losses kick in when you can't go higher and you are
still burning fuel. Using one 50th of the Shuttle's fuel to go to
100,000 feet is no loss if you still have enough fuel at 100,000 feet
to get your air-launched vehicle to orbit

Finally, winged vehicles are much
less efficient on the final orbital insertion burn; the dry mass is
very significantly increased by the presence of wings- this makes the
final insertion burn require multiple times more fuel.


Dry mass just "is". It is not more or less detrimental for it to be
wings than it is to be anvils in the cargo bay. Wings are only
significant help or hinderence where there is air. Where there is no
air it doesn't matter what shape of appendages are sticking out.

Thin air continues to provide lift if the speed is high enough, and the
speed gets higher the thinner the air because of less air drag, so that
works out splendidly all the way around. As the air gets too thin for
lift it gets too thin for appreciable drag also.

The fuel is not the problem. The oxidizer is the problem because it
weighs so much. Oxygen weighs 16 atomic weight units for ever 1 of
Hydrogen. NASA's Shuttle expends a million pounds of fuel and oxidizer
to get the first 100,000 feet, the same altitude they got with 28
horsepower of electric motors turning propellers shovelling air,
powered by solar cells.

http://en.wikipedia.org/wiki/Earth%27s_atmosphere
"An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where
atmospheric effects become noticeable during re-entry. The Karman line,
at 100 km (62 mi), is also frequently used as the boundary between
atmosphere and space."

One can assume the reverse is true: if atmosphere friction becomes
noticeable at 120 km, than wings are still providing some lift so long
as the speed is high enough to invoke Newton's Law of equal and
opposite reactions.


Unless you are using an airbreathing engine it's all at best a wash or
only very modest improvements indeed.

They also enable a spacecraft to 'fly' to a runway and land
softly after deorbit.


Yes, although landing speeds can be very high.


Because the wings are too small. More wings mean slower descent. Yes
it's hot at first by there's soon a cold high strata which can shed
that heat by flying around in it for a while in a mostly empty
spaceplane with lot's of glide lift. They soft land capsules with
parafoils made of cloth, and they do it on Mars where the air is as
thin as it is at 100,000 feet. There's no reason a big like kite-like
spaceplane can't soft-land on it's airport of choice.


The proof that wings gain an advantage is that a bomber can reach
20,000 feet and stay there for the hours it takes to reach target and
return on 1/10th of the thrust to weight ratio that a vertical tubular
rocket requires just to slowly leave the launch pad.


Yes, although that is more to do with high ISP of airbreathing engines
and the high lift/drag ratio that is achievable only at low speeds.


Again, jets don't have to carry their oxidizer. High lift is
proportional to Newton's law, not speed. It has to do with collisions
of air molecules from the surfaces of the travelling aircraft. When
there is significantly more lift on the undersurfaces than above, the
craft flies, otherwise it sinks.

Waverider vehicles are intended to ride on hypersonic compression lift
and do it above mach 8.
http://en.wikipedia.org/wiki/Waverider

Where there is not enough air to collide with the undersurfaces there
is no lift and likewise no drag either. Then the only force is Newton's
law applying to propellent exhaust.


Today, however, a waverider design shouldn't be all that difficult with
the knowledge and materials base that exists in 2006. Titanium is
plentiful and easily worked. The SSME (Space Shuttle Main Engine) has
proven to be reliable. The tile problem has been solved (Don't tell
NASA -- they haven't found out yet.). And, slush hydrogen tanks have
solved the volume problem for hypergolic hydrogen/lox burners like the
SSME.


All those things were known about when the Shuttle was built. It's not
that simple.


Right. It's not simple. Nobody, not the superpowers, not the second
tier nations, not the biggest corporations nor the smallest, has ever
launched a SSTO to LEO and back.

SpaceShipOne only got 1/3rd the way there and that wasn't SSTO, it was
two staged, carried on White Knight.

Wings are cheaper than fuel. Before last year's oil price gouging
carbon-fiber fabric was down to $0.94 square foot for 6kx6k 2,000,000
psi, wholesale in volume lots. The cost of 10,000 square feet of wings
in material costs was less than buying a Piper Cub used. Now Exxon got
their price raise and it costs a NEW Piper Cub.

There's a lot of pnoney baloney on the internet about how cheap H2 and
O2 is. Some say NASA pays $0.08 a kilogram for LOX, but that doesn't
add up. Just trucking it from Mississippi to KSC in 4,000 gallon
tankers has to cost $1/gallon for shipping, or do you believe in the
"fuel fairy" giving away fuel below costs?

Somebody needs to do a price breakdown on the price of a Shuttle
launch: prices from $1.2 billion to $55 million are tossed around, with
$500 million per launch being the favorite of more people. NASA
themselves says that the cost of payload is $10,000 per pound. Five
kilos of drinking water for the ISS would buy 10,000 square feet of
wing material. There's probably more than 10,000 square feet of wing
material in that big External Tank they throw away each launch.

More Wings, Less Fuel. If you have to think BIG, think BIG about stuff
you don't throw away every launch instead of big fuel bills and big
disposible tanks.

  #15  
Old February 26th 06, 02:56 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago


H2-PV NOW wrote:
The fuel is not the problem. The oxidizer is the problem because it
weighs so much.


No, that's not really a problem. After all, you're throwing it away
during flight, and rocket engines are light for the thrust they
deliver. Much lighter than propellers, wings, and jet engines.

Wings are cheaper than fuel. Before last year's oil price gouging
carbon-fiber fabric was down to $0.94 square foot for 6kx6k 2,000,000
psi, wholesale in volume lots. The cost of 10,000 square feet of wings
in material costs was less than buying a Piper Cub used. Now Exxon got
their price raise and it costs a NEW Piper Cub.

There's a lot of pnoney baloney on the internet about how cheap H2 and
O2 is.


Funny, you also just used some very dubious accounting.

Have you looked at the price it takes to build a wing once you factor
in research and development, labor, and all other costs that go into
the final price tag? The material cost of the space shuttle, or 747, or
F22, is a trivial cost component. I assure you, the F22 isn't $130
million because of the materials costs. In fact, it's noteworthy how
the F22's price drops as the production quantities go up.

Carbon material prices...

I recently (2004) priced out a custom-made carbon-epoxy case for some
electronics. The prototype would've run about $3000, with $100 of that
being off-the-shelf materials the composite firm had in stock (and
trust me, they were marking up the materials prices.) Get some
carbon-epoxy board from the warehouse, cut to shape, glue together -
simple, fast, and $3000 once you got done paying for the engineering
and assembly labor. It was a crude demonstrator unfit for service, just
something to show to the client.

Incidentally, I settled on a modified off-the-shelf aluminum case.
Thin, stamped sheet aluminum using existing molds and, actually, fewer
cutting operations than the basic case. Price: $8000, and it wasn't for
the cost of the sheet aluminum ($20).

I've made carbon-carbon composites, simple shapes that would be
suitable for brake pads. The cost of the carbon fiber was, as you
noted, cheap. In 3 hours of running the CVD furnace, we burned $500 in
electricity to produce a hocky puck-sized piece of carbon-carbon,
nevermind the hours of labor spent setting up the furnace, making the
carbon fiber preforms, paying the bureaucracy that supported the
research lab. (All those extra expenses were worked into the overall
labor cost - I only wish I made $100/hour like we billed.) In fact,
most C-C production can take a couple of weeks in a furnace, not 3
hours, with interruptions for machinists to carve off crusts.

$0.94 per square foot of material is a number that has NOTHING to do
with the cost of a wing. It's a footnote some junior clerk will
scribble in under labor, overhead, and tooling costs.

Some say NASA pays $0.08 a kilogram for LOX, but that doesn't
add up. Just trucking it from Mississippi to KSC in 4,000 gallon
tankers has to cost $1/gallon for shipping, or do you believe in the
"fuel fairy" giving away fuel below costs?


Why don't you send Praxair or Air Liquide an email and ask what a
4000-gallon LOX delivery to your front door costs?

I really doubt the LOX will be shipped from Mississippi, though. Most
major industrial gas distributers have production facilities in every
state, and will offer to hook you up with an on-site LOX production
unit if your demand is high enough.

Somebody needs to do a price breakdown on the price of a Shuttle
launch: prices from $1.2 billion to $55 million are tossed around, with
$500 million per launch being the favorite of more people.


$55 million is about the cost of direct expenses for launching the
shuttle - including the fuel. $500 million is about the cost when NASA
gets done billing for labor for its army of workers.

More Wings, Less Fuel. If you have to think BIG, think BIG about stuff
you don't throw away every launch instead of big fuel bills and big
disposible tanks.


If you launch the same vehicle over and over, perhaps several dozen
times per year, yeah, the fuel might get to be an issue. Until then,
it's still an inexpensive component of operating a spacecraft. Adding
several billion dollars to the expense of engineering a vehicle to have
wings is another issue.

Mike Miller, Materials Engineer

  #16  
Old February 27th 06, 07:52 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

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H2-PV NOW wrote:
[...]
Not necessarily: NASA Helios Prototype flew to 96,863 feet in 2001
using propellers shovelling air powered by 28 horsepower motors fueled
by sunlight from solar cells on it's wings.


Yes; *very slowly*, which makes it entirely irrelevant when dealing with
orbital vehicles. The thing is...

[...]
You don't mind thinking big about fuel expendatures and thinking big
about money expendatures -- try thinking BIG about wings.

[...]
Skylon has stubby little wings, which is why its
projected payload is so low.


...big wings mean big drag. For the kind of velocities you need to get into
orbit, big drag is fatal. Not only will you have to burn fuel in order to
counter the drag, but as soon as you get above the point where the wings
help give you lift, you end up having to carry them by sheer rocket power
- --- which is a waste. And since you reach that point very quickly, it's
generally not considered worth the effort.

Forgive me for saying so, I think you're still under the impression that
going high is sufficient to get into orbit. It's not, and in fact it's
largely irrelevant. Orbit's all about going *fast*. You can't go fast in an
atmosphere.

[...]
There is no such thing as "gravity losses" as long as a vehicle is
ascending. Gravity losses kick in when you can't go higher and you are
still burning fuel.


I'm sorry, but this is simply incorrect. Gravity losses apply all the time
your vehicle is in the air. Gravity is continuously trying to accelerate
your vehicle downwards at 9.8 m/s/s; you have to apply, at minimum, enough
force to counter that. If your rocket is sufficient to accelerate your
vehicle in at 10 m/s/s in flat space, then under gravity you're only going
to accelerate upwards at 0.2 m/s/s --- most of your thrust is being wasted.
Those are gravity losses.

[...]
Dry mass just "is". It is not more or less detrimental for it to be
wings than it is to be anvils in the cargo bay. Wings are only
significant help or hinderence where there is air. Where there is no
air it doesn't matter what shape of appendages are sticking out.


On the contrary --- customers are paying you to lift those anvils, but
they're not paying you to lift the wings. Every kilo of unnecessary
structure is one kilo of cargo you can't carry. Wings are unavoidably
heavy; they're a crucial part of your vehicle's stress structure.

[...]
One can assume the reverse is true: if atmosphere friction becomes
noticeable at 120 km, than wings are still providing some lift so long
as the speed is high enough to invoke Newton's Law of equal and
opposite reactions.


*nods*

...except, wings *only* work if they're interacting with the atmosphere,
which means drag. That's how they work. If your wings didn't have any drag,
they wouldn't give you any lift, by definition. So, you're going to have to
burn fuel to counter that drag. Wings are only useful if:

(fuel needed to power wings when in atmosphere) +
(fuel needed to lift wings when above atmosphere)

is less then:

(fuel saved by having wings)

With current state-of-the art, this is not the case, and given that most
spacecraft are in the atmosphere for a very brief amount of time --- for
the space shuttle, this is about two minutes --- it's not considered worth
the hassle.

[...]
Waverider vehicles are intended to ride on hypersonic compression lift
and do it above mach 8.


You should look into what engines are available that will breathe air at
mach 8; currently the total number is 0. Air-breathing hypersonic engines
are very, very hard, largely due to the fact that you have to slow the air
down enough so that your engine can interact with it. This involves drag,
and lots of it, which means your engine has to produce enough thrust to
counter the drag, and frankly the added weight and complexity mean that
again, it's not worth the hassle. Particularly since once you're above the
atmosphere you're going to have to lift all that dead weight with your
conventional rockets, which you're going to have to carry anyway.

[...]
SpaceShipOne only got 1/3rd the way there and that wasn't SSTO, it was
two staged, carried on White Knight.


No. No, it didn't. SS1 reached Mach 3. Orbit is about the equivalent of Mach
25. That's 1/8 of the way.

- --
+- David Given --McQ-+ "Hydrogen fusion, the sun makes shine
| | Vascular pressure makes the ivy twine.
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  #17  
Old February 28th 06, 11:18 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago


"H2-PV NOW" wrote in message
oups.com...
Ian Woollard wrote:
In
addition, because it spends more time to reach orbit, the gravity
losses are higher; although they are offset by the higher efficiencies
of wings at supporting the vehicle.


There is no such thing as "gravity losses" as long as a vehicle is
ascending. Gravity losses kick in when you can't go higher and you are
still burning fuel. Using one 50th of the Shuttle's fuel to go to
100,000 feet is no loss if you still have enough fuel at 100,000 feet
to get your air-launched vehicle to orbit


You're showing your ignorance here and are handwaving away a very basic part
of the equation. There most certainly are gravity losses even if the
vehicle is ascending. Essentially, the slower you accellerate to orbital
altitude *and* velocity, the higher your gravity losses will be.

The fuel is not the problem. The oxidizer is the problem because it
weighs so much. Oxygen weighs 16 atomic weight units for ever 1 of
Hydrogen. NASA's Shuttle expends a million pounds of fuel and oxidizer
to get the first 100,000 feet, the same altitude they got with 28
horsepower of electric motors turning propellers shovelling air,
powered by solar cells.


But the shuttle is moving at considerably higher velocity at 100k feet.

More importantly, spending time in the atmosphere to "save" on the mass of
LOX is silly if your goal is to get to LEO, especially considering that LOX
is one of the cheapest fluids on the planet since it's literally made from
air.

Wings are cheaper than fuel. Before last year's oil price gouging
carbon-fiber fabric was down to $0.94 square foot for 6kx6k 2,000,000
psi, wholesale in volume lots. The cost of 10,000 square feet of wings
in material costs was less than buying a Piper Cub used. Now Exxon got
their price raise and it costs a NEW Piper Cub.


You're showing your ignorance again. $0.94 per square foot for carbon fiber
fabric isn't what's expensive. It's the cost of the machines, labor, and
time it takes to turn that into a wing that kills you. More than one friend
of mine used to work for a US company that makes carbon fiber tape laying
machines. Just writing the programs to lay the tape isn't easy...

There's a lot of pnoney baloney on the internet about how cheap H2 and
O2 is. Some say NASA pays $0.08 a kilogram for LOX, but that doesn't
add up. Just trucking it from Mississippi to KSC in 4,000 gallon
tankers has to cost $1/gallon for shipping, or do you believe in the
"fuel fairy" giving away fuel below costs?


Look again at launch prices (i.e. $ per lb to LEO) and compare them to the
price of fuel ($ for fuel to get 1 lb to LEO). It's not the high price of
fuel that is keeping launch costs so high.

Somebody needs to do a price breakdown on the price of a Shuttle
launch: prices from $1.2 billion to $55 million are tossed around, with
$500 million per launch being the favorite of more people. NASA
themselves says that the cost of payload is $10,000 per pound. Five
kilos of drinking water for the ISS would buy 10,000 square feet of
wing material. There's probably more than 10,000 square feet of wing
material in that big External Tank they throw away each launch.


The ET's LOX tank holds about 20,000 cubic feet of LOX. A quick search says
LOX weighs 64 lb per cubic foot, giving you 1,280,000 lbs of LOX in the ET.
If a shuttle launch costs $500 million, LOX would need to cost you about $4
per lb to make up just 1% of the total cost to launch the shuttle. Actual
cost for LOX production (minus transportation costs) is reportedly pennies
per pound. Even rocket grade kerosene costs you less than $4 per lb.

Here's part of an old (1996) posting from Henry Spencer:

begin old posting

If using LOX/kerosene, you need about 20 pounds of mix to lift a pound
into orbit, and maybe, oh, a fifth of those pounds are payload, so you
need 100 pounds of fuel+oxidizer. Now, LOX costs about 4c/pound, and
is about 3/4 of the mix. Kerosene costs depend on grade, but expensive
rocket-grade stuff is maybe 25c/pound. So the average mix cost is
circa 10c/pound, and total propellant costs are about $10 per pound of
payload.

Figuring me at 200 pounds, that's $2000. Not quite as cheap as London to
New York, agreed, but not much more than what I paid for a round trip from
Toronto to Australia some years ago.

end old posting

In other words, the high cost of fuel isn't what makes spaceflight expensive
when launch costs fare more than the cost of fuel for the launch.

Now tell us again how the high price of LOX is making launch costs so high.
:-)

Jeff
--
Remove icky phrase from email address to get a valid address.


  #18  
Old March 15th 06, 08:41 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

Various attempts have been made to design hypersonic airbreathing
engines. The X-43 is probably the only one to fly, even briefly. The
problem with scramjets is that they tend to be efficient only in a
narrow range of speeds; great for a cruise missile but not for orbital
launch. The liquid air cycle (i.e. hotol) is less speed sensitive but
there's no easy way to carry enough cooling capacity to actually
liquify all the air you need. Best bet might essentially be a
cooled-inlet turbojet. Wings can be useful for thrust-limited designs,
but a launch vehicle goes through the speed regiemes quickly and above
about 30 KM wings aren't much use. After attacking the SSTO problem
for awhile, at some point a two-stage solution begins to look more
practical.

  #19  
Old March 15th 06, 08:42 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

In other words, the high cost of fuel isn't what makes spaceflight expensive
when launch costs fare more than the cost of fuel for the launch.

Exactly. Almost all the cost for the Shuttle is the maintenance needed
between flights. Some parts, like the SRBs, are completely
disassembled, stripped to bare metal (even the nuts and bolts),
inspected for cracks, and remanufactured. The Orbiter requires months
of inspections and maintenance. But these aren't the inevitable result
of the vehicle being reusable; they're with us because the Shuttle was
designed before we had any actual flight experience with many of the
critical systems, particularly the TPS and SRBs. Analysis is not
equivalent to experience; the predictions of operating cost and
reliability were off by a factor of at least 10. The technology
demonstrators (X-33, X-34, DC-X, X-37) would have provided the flight
experience to do it better next time.

But we are about to learn the wrong lesson. Instead of taking what
we've learned and designing a reusable launch vehicle that is practical
and safe, we have decided that reusable spacecraft are by nature
expensive and unreliable.

  #20  
Old March 15th 06, 08:42 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

In article ,
David Given wrote:

[...]
SpaceShipOne only got 1/3rd the way there and that wasn't SSTO, it was
two staged, carried on White Knight.


No. No, it didn't. SS1 reached Mach 3. Orbit is about the equivalent of Mach
25. That's 1/8 of the way.


Actually it much worse than 1/8 of the way. In terms of energy that
eight to one velocity increase takes 128 times more energy. As you can
see SpaceShipOne was far from getting to orbit.

--
Mike Swift

Two things only the people anxiously desire‹bread and circuses.
Decimus Junius Juvenalls
 




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