speed record set by scramjet - fair?

With so little air friction at 100,000 feet, a stone would go quite
far. Give it an aerodynamic shape and it would go even further. I
would only be guessing, but maybe it would go a few hundred miles.

The point is that almost any craft with a propulsion system capable of
moving it at 700 miles per hour would make it to Mach 10 when dropped
from a rocket going Mach 9, provided it was structurally sound enough.
It just sounds to me like an accomplishment that was not in
proportion to the media it got. But I am not an aeronautical engineer
by any stretch of the imagination. So, maybe it really was an
incredible accomplishment and I just don't understand why.

Aardvark wrote in message ...
Don French wrote:

How fast was the rocket going when it released the record-setting
scramjet? If the rocket was going Mach 9 in the thin atmosphere at
100,000 feet and released a stone, for example, the stone would travel
several seconds at close to Mach 9. I assume that the rocket was not
going Mach 9, but I haven't seen any information on how fast it was
going.

Regardless, it seems to me that the rocket's speed has to be
subtracted from the jet's speed to arrive at the actual jet speed when
you talk about the world's record for speed of a jet plane.

-- Don French
Quoted from some web site.

"The telemetry showed the X-43A was set free by the booster at a speed
well in excess of Mach 9 but was able to maintain its cruising velocity
under the thrust from its scramjet.

Engineers followed the X-43A as it travelled more than 1,000km (620
miles), eventually losing speed and plunging into the Pacific. "

Now if the rock went 620 miles after release

"Don French" wrote in message
om...
With so little air friction at 100,000 feet, a stone would go quite
far. Give it an aerodynamic shape and it would go even further. I
would only be guessing, but maybe it would go a few hundred miles.

The point is that almost any craft with a propulsion system capable of
moving it at 700 miles per hour would make it to Mach 10 when dropped
from a rocket going Mach 9, provided it was structurally sound enough.

This thread is hilarious. A bunch of armchair propulsion engineers
pooh-poohing a significant accomplishment in engine technology, none of whom
actually could design a scramjet if their lives depended on it.

Anyway, I certainly think NASA is well within their rights to tout the
success of actually operating a scramjet in flight. It's as revolutionary
as successful operation of the first turbine engine was. What makes the
speed interesting is that no other engine is capable of operating at that
speed. Even if the test vehicle didn't wind up ANY faster than it was when
the engine was started, as long as the engine continued to operate as
designed, it would have been a successful test.

Pete

I never said it wasn't a successful test, but the only thing touted in
the media was the speed it achieved and the world record it set for
speed, and attributed that speed to the scramjet, not the rocket.
That was just wrong. The speed was almost entirely a result of the
rocket's velocity and had nothing to do with the scramjet. Seriously,
they could have dropped a Piper cub off that rocket and it could have
maintained Mach 9 for hundreds of miles. Should it get the world's
speed record for prop-driven planes? I think not. And I think that
giving the X-43A a worlds speed record is just as fraudulent.

With so little air friction at 100,000 feet, a stone would go quite
far. Give it an aerodynamic shape and it would go even further. I
would only be guessing, but maybe it would go a few hundred miles.

The point is that almost any craft with a propulsion system capable of
moving it at 700 miles per hour would make it to Mach 10 when dropped
from a rocket going Mach 9, provided it was structurally sound enough.

This thread is hilarious. A bunch of armchair propulsion engineers
pooh-poohing a significant accomplishment in engine technology, none of whom
actually could design a scramjet if their lives depended on it.

Anyway, I certainly think NASA is well within their rights to tout the
success of actually operating a scramjet in flight. It's as revolutionary
as successful operation of the first turbine engine was. What makes the
speed interesting is that no other engine is capable of operating at that
speed. Even if the test vehicle didn't wind up ANY faster than it was when
the engine was started, as long as the engine continued to operate as
designed, it would have been a successful test.

Pete

"Don French" wrote in message
om...
I never said it wasn't a successful test, but the only thing touted in
the media was the speed it achieved and the world record it set for
speed

Who cares what the media says? If you know anything about aviation, you
know as well as the rest of us that the media does a pretty poor job of
getting facts straight, especially for technical issues like this one.

and attributed that speed to the scramjet, not the rocket.
That was just wrong. The speed was almost entirely a result of the
rocket's velocity and had nothing to do with the scramjet.

Todd already pointed out the fallacy of that statement. The fact that the
scramjet *accelerated* to the maximum speed clearly shows that the scramjet
is, in fact, the *entire* source of the speed. It produced enough thrust to
maintain Mach 10.

Your statement is like saying that if you towed a Y*go behind a Porsche and
got it up to 150 mph, that you'd be able to then simply disconnect from the
Porsche and still maintain 150 mph in the Y*go. That's simply not true. A
vehicle that can accelerate to Mach 10 from *any* speed and maintain that
speed is capable, all by itself, of that speed. It's just plain incorrect
to claim that "only the last Mach was due to the scramjet" (or however you'd
like to word it).

Seriously,
they could have dropped a Piper cub off that rocket and it could have
maintained Mach 9 for hundreds of miles.

Hundreds? I doubt it. But more importantly, it would NOT have accelerated
to Mach 10.

Should it get the world's
speed record for prop-driven planes?

In your example, the Piper Cub at no point *maintained* a record-breaking
speed.

I think not. And I think that
giving the X-43A a worlds speed record is just as fraudulent.

Well, I'm sorry your incomplete grasp of the facts makes you think that.
Fortunately, those who have a say in the matter have a better understanding
of the situation.

Pete

Peter,

You apparently never took high school physics. Look up Newton's first
law of motion, the law of inertia. The scramjet only had to provide
enough power to overcome the friction of air to continue at Mach 9.5
forever or until it hit something, like the earth. To accererate the
jet from Mach 9.5 to Mach 10 takes exactly the same amount of power as
accerating from 0 mph to Mach 0.5, not very much. And that is all that
the scramjet did.

Yes, if you towed a Yugo behind a Porsche, and released it at 150 mph,
it would continue at 150 mph if there were no friction of air and
road. But it could not accelerate to 180 because the means of
propulsion depend on that same friction, unlike a jet plane, which
does not use the friction, but only has to overcome it.

This is elementary physics, a subject that it seems fewer and fewer
people have a grasp of these days.

As to the media, yes I know the media gets almost everything wrong.
But the speed record claim was the topic of my post, not whether there
was a significant accomplishment in running a scramjet in an aircraft
going Mach 10.

-- Don French

I never said it wasn't a successful test, but the only thing touted in
the media was the speed it achieved and the world record it set for
speed

Who cares what the media says? If you know anything about aviation, you
know as well as the rest of us that the media does a pretty poor job of
getting facts straight, especially for technical issues like this one.

and attributed that speed to the scramjet, not the rocket.
That was just wrong. The speed was almost entirely a result of the
rocket's velocity and had nothing to do with the scramjet.

Todd already pointed out the fallacy of that statement. The fact that the
scramjet *accelerated* to the maximum speed clearly shows that the scramjet
is, in fact, the *entire* source of the speed. It produced enough thrust to
maintain Mach 10.

Your statement is like saying that if you towed a Y*go behind a Porsche and
got it up to 150 mph, that you'd be able to then simply disconnect from the
Porsche and still maintain 150 mph in the Y*go. That's simply not true. A
vehicle that can accelerate to Mach 10 from *any* speed and maintain that
speed is capable, all by itself, of that speed. It's just plain incorrect
to claim that "only the last Mach was due to the scramjet" (or however you'd
like to word it).

Seriously,
they could have dropped a Piper cub off that rocket and it could have
maintained Mach 9 for hundreds of miles.

Hundreds? I doubt it. But more importantly, it would NOT have accelerated
to Mach 10.

Should it get the world's
speed record for prop-driven planes?

In your example, the Piper Cub at no point *maintained* a record-breaking
speed.

I think not. And I think that
giving the X-43A a worlds speed record is just as fraudulent.

Well, I'm sorry your incomplete grasp of the facts makes you think that.
Fortunately, those who have a say in the matter have a better understanding
of the situation.

Pete

(Don French) wrote:

Peter,

You apparently never took high school physics.
Pot calling the kettle black?

Look up Newton's first
law of motion, the law of inertia. The scramjet only had to provide
enough power to overcome the friction of air to continue at Mach 9.5
forever or until it hit something, like the earth.
Odd use of the word "only". Like "only" 850-odd times as much power as
it takes to fly at Mach 1. Or does the velocity cubed relationship not
apply for air friction in supersonic flight?

To accererate the
jet from Mach 9.5 to Mach 10 takes exactly the same amount of power as
accerating from 0 mph to Mach 0.5, not very much. And that is all that
the scramjet did.
BZZZT! It takes a little more power (how much more determines how
rapid the acceleration will be) to accelerate from 0 to Mach0.5 than
it takes to maintain Mach 0.5. It takes a little more power to
accelerate from 9.5 to 10 than it takes to maintain 10. And using the
cube rule, it takes 8000 times as much power to maintain mach 10 as it
does to maintain mach 0.5.

Yes, if you towed a Yugo behind a Porsche, and released it at 150 mph,
it would continue at 150 mph if there were no friction of air and
road. But it could not accelerate to 180 because the means of
propulsion depend on that same friction,
No. It has the means of friction (it's tires are on the road, at least
in this thought experiment; I'd hate to think about it in real
lifeg), just not enough power to overcome drag at 150, much less to
accelerate from that point.

unlike a jet plane, which
does not use the friction, but only has to overcome it.

This is elementary physics, a subject that it seems fewer and fewer
people have a grasp of these days.
Yes, so it seems!


--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

In article , alexy wrote:
(Don French) wrote:

You apparently never took high school physics.
Pot calling the kettle black?

On the contrary, it would seem that he did attend highschool physics,
got a C, and stopped there. :-)


Morris (considering the sperical cow)

"Don French" wrote in message
om...
You apparently never took high school physics.

Right back at ya'.

Look up Newton's first law of motion, the law of inertia.

The law of inertia has nothing to do with this.

The scramjet only had to provide
enough power to overcome the friction of air to continue at Mach 9.5
forever or until it hit something, like the earth.

In aircraft, that power is everything. Inertia provides very little support
to flight, and especially for light aircraft (like those we fly) and for
extremely fast aircraft (like the scramjet equipped test vehicle). And the
power required is the same whether you start at 0 mph or Mach 9.

To accererate the
jet from Mach 9.5 to Mach 10 takes exactly the same amount of power as
accerating from 0 mph to Mach 0.5, not very much.

You are absolutely wrong on this point. The drag at Mach 9.5 is vastly
larger than the drag at 0 mph, and as such requires vastly greater amounts
of power to accomplish any acceleration. Nearly all of the power invested
is used to overcome drag, not inertia.

And that is all that the scramjet did.

"All". Yes, you continue to demonstrate your lack of knowledge on this
point.

Yes, if you towed a Yugo behind a Porsche, and released it at 150 mph,
it would continue at 150 mph if there were no friction of air and
road.

But there IS friction. In this scenario, the friction dominates the physics
completely. Your frictionless scenario is completely irrelevant.

But it could not accelerate to 180 because the means of
propulsion depend on that same friction, unlike a jet plane, which
does not use the friction, but only has to overcome it.

Again, your frictionless scenario is completely irrelevant.

This is elementary physics, a subject that it seems fewer and fewer
people have a grasp of these days.

Yes, you are demonstrating that quite well.

Pete

Look up Newton's first law of motion, the law of inertia.

The law of inertia has nothing to do with this.

The law of inertia has nothing to do with this? It has everything to
do with it. It is usually stated thusly: An object at rest tends to
stay at rest and an object in motion tends to stay in motion with the
same speed and in the same direction unless acted upon by an
unbalanced force.

In this case, if you dropped anything at all out of that rocket at
Mach 9.5, it would contine to move at Mach 9.5 forever unless acted
upon. The jet would never have to fire its engines and it would
maintain Mach 9.5 if it weren't for the effect of air friction, the
unbalanced force. In a vacuum, the thrust required to accelerate from
Mach 0.5 to 1.0 is exactly the same force required to accelerate from
Mach 9.5 to Mach 10.0.


To accererate the
jet from Mach 9.5 to Mach 10 takes exactly the same amount of power as
accerating from 0 mph to Mach 0.5, not very much.

You are absolutely wrong on this point. The drag at Mach 9.5 is vastly
larger than the drag at 0 mph, and as such requires vastly greater amounts
of power to accomplish any acceleration. Nearly all of the power invested
is used to overcome drag, not inertia.

I see part of the problem. You, like many non-technical people, think
that inertia is only something to overcome. Inertia is as much about
the difficulty in slowing something down as it speeding something up.
I understand why you were confused about that, though, because in
common non-technical usage, the word is almost only used to mean hard
to get going, not hard to stop. But it is also inertia that keeps
objects moving.

For what it is worth, there isn't a lot of air at 100,000 feet. If I
am not mistaken, the density of air at 100,000 feet is 1/400 the air
density at 5000 feet. It is pretty thin, so that also has to be taken
into consideration when evaluating the accomplishment.



But there IS friction. In this scenario, the friction dominates the physics
completely. Your frictionless scenario is completely irrelevant.

The frictionless scenario is the starting point for understanding the
problem. Once you undersand that the plane would fly at the rocket's
speed without an engine if there were no air resistance, you can limit
the problem to analyzing the power it takes to overcome friction.
However, I admit that I did not know the velocity cubed rule. I don't
think it is basic high school physics like the first law of motion is,
but I didn't know it. I was under the impression that the relationship
between velocity and drag was linear. I never studied fluid dynamics
and made a wrong assumption. My bad. That made my comparison between
accelerating from 0.5 to 1.0 versus 9.5 to 10.0 incorrect. It makes
the achievement of the scramjet more impressive than I thought.
Thanks for educating me.


i.

This is elementary physics, a subject that it seems fewer and fewer
people have a grasp of these days.

Yes, you are demonstrating that quite well.

Well, I wasn't trying to personalize my statement and I don't think
you really needed to either. My statement is in fact true. Less and
less people have a grasp of physics these days. In point of fact, I
have a very old bachelor's degree in physical chemistry, which is not
physics per se, but I did study mechanics, if not fluid dynamics.

-- Don French


Pete

Look up Newton's first law of motion, the law of inertia.

The law of inertia has nothing to do with this.

The law of inertia has nothing to do with this? It has everything to
do with it. It is usually stated thusly: An object at rest tends to
stay at rest and an object in motion tends to stay in motion with the
same speed and in the same direction unless acted upon by an
unbalanced force.

In this case, if you dropped anything at all out of that rocket at
Mach 9.5, it would contine to move at Mach 9.5 forever unless acted
upon. The jet would never have to fire its engines and it would
maintain Mach 9.5 if it weren't for the effect of air friction, the
unbalanced force. In a vacuum, the thrust required to accelerate from
Mach 0.5 to 1.0 is exactly the same force required to accelerate from
Mach 9.5 to Mach 10.0.


To accererate the
jet from Mach 9.5 to Mach 10 takes exactly the same amount of power as
accerating from 0 mph to Mach 0.5, not very much.

You are absolutely wrong on this point. The drag at Mach 9.5 is vastly
larger than the drag at 0 mph, and as such requires vastly greater amounts
of power to accomplish any acceleration. Nearly all of the power invested
is used to overcome drag, not inertia.

I see part of the problem. You, like many non-technical people, think
that inertia is only something to overcome. Inertia is as much about
the difficulty in slowing something down as it speeding something up.
I understand why you were confused about that, though, because in
common non-technical usage, the word is almost only used to mean hard
to get going, not hard to stop. But it is also inertia that keeps
objects moving.

For what it is worth, there isn't a lot of air at 100,000 feet. If I
am not mistaken, the density of air at 100,000 feet is 1/400 the air
density at 5000 feet. It is pretty thin, so that also has to be taken
into consideration when evaluating the accomplishment.



But there IS friction. In this scenario, the friction dominates the physics
completely. Your frictionless scenario is completely irrelevant.

The frictionless scenario is the starting point for understanding the
problem. Once you undersand that the plane would fly at the rocket's
speed without an engine if there were no air resistance, you can limit
the problem to analyzing the power it takes to overcome friction.
However, I admit that I did not know the velocity cubed rule. I don't
think it is basic high school physics like the first law of motion is,
but I didn't know it. I was under the impression that the relationship
between velocity and drag was linear. I never studied fluid dynamics
and made a wrong assumption. My bad. That made my comparison between
accelerating from 0.5 to 1.0 versus 9.5 to 10.0 incorrect. It makes
the achievement of the scramjet more impressive than I thought.
Thanks for educating me.


i.

This is elementary physics, a subject that it seems fewer and fewer
people have a grasp of these days.

Yes, you are demonstrating that quite well.

Well, I wasn't trying to personalize my statement and I don't think
you really needed to either. My statement is in fact true. Less and
less people have a grasp of physics these days. In point of fact, I
have a very old bachelor's degree in physical chemistry, which is not
physics per se, but I did study mechanics, if not fluid dynamics.

-- Don French


Pete