speed record set by scramjet - fair?

[Don French]

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

[gatt]

"Don French" > wrote in message

> 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.

Hmm. Would you say the same for Yeager and the X-1, it having been dropped
from the belly of another aircraft, or is your particular question related
just to the rocket?

Would this same sort of criteria apply to the X-prize given that Space Ship
One was given a lift to an intermediate altitide?

Interesting.
-c

[Bob Gardner]

The press report I read said that the scramjet wouldn't even start below
Mach 4.0.

Bob Gardner

"Don French" > wrote in message
om...
> 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

[Nathan Gilliatt]

In article >,
"gatt" > wrote:

> Would this same sort of criteria apply to the X-prize given that Space Ship
> One was given a lift to an intermediate altitide?

You could interpret the White Knight as a manned first stage of the
launch system. Since it's also reusable within the prize parameters, the
complete launch system would still qualify.

Whether or not you subtract the rocket's speed from the X-43, it's still
quite an accomplishment to have an air-breathing engine running at Mach
10. This is the proof of concept stage, right? Now we know that the
scramjet design doesn't just blow itself out.

- Nathan

[Aardvark]

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 :)

[Nathan Young]

On Wed, 17 Nov 2004 18:22:14 -0500, Aardvark
> wrote:

>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 :)

That's interesting. I wonder how far it would have glided without
lighting the scramjet. At mach 9, the miles go by pretty quickly...

[Jay Honeck]

> 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.

On a deeper level, I find the enthusiasm about this scramjet flight to be,
in many ways, pathetic.

I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
flight here -- which is somehow trumped up to be some sort of a huge success
for NASA? Worse, they're claming that they've "beaten the speed record set
by the X-15 some 40 years ago..."

Compare this sad little program to the heady days of the manned X-15, with
dozens of suborbital flights over a period of years, and you soon see what I
mean. It's hard to watch this new generation getting all excited about a
program that, in the 1960s, wouldn't have merited mention on the nightly
news.

But I suppose that's all they really have to get excited about nowadays,
with the space program completely shut down.

NASA has sunk so far since I was a boy...it is to weep.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Wizard of Draws]

On 11/17/04 9:47 PM, in article 03Umd.45151$V41.23702@attbi_s52, "Jay
Honeck" > wrote:

>
> On a deeper level, I find the enthusiasm about this scramjet flight to be,
> in many ways, pathetic.
>
> I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
> flight here -- which is somehow trumped up to be some sort of a huge success
> for NASA? Worse, they're claming that they've "beaten the speed record set
> by the X-15 some 40 years ago..."
>
> Compare this sad little program to the heady days of the manned X-15, with
> dozens of suborbital flights over a period of years, and you soon see what I
> mean. It's hard to watch this new generation getting all excited about a
> program that, in the 1960s, wouldn't have merited mention on the nightly
> news.
>
> But I suppose that's all they really have to get excited about nowadays,
> with the space program completely shut down.
>
> NASA has sunk so far since I was a boy...it is to weep.

I feel the same way. I have a hard time calling the thing a plane since it's
unmanned. In my mind, a plane has a pilot sitting at the controls.
--
Jeff 'The Wizard of Draws' Bucchino
Cartoons with a Touch of Magic�
http://www.wizardofdraws.com
http://www.cartoonclipart.com

[Mike Rapoport]

"Jay Honeck" > wrote in message
news:03Umd.45151$V41.23702@attbi_s52...
>> 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.
>
> On a deeper level, I find the enthusiasm about this scramjet flight to be,
> in many ways, pathetic.
>
> I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10
> second flight here -- which is somehow trumped up to be some sort of a
> huge success for NASA? Worse, they're claming that they've "beaten the
> speed record set by the X-15 some 40 years ago..."
>
> Compare this sad little program to the heady days of the manned X-15, with
> dozens of suborbital flights over a period of years, and you soon see what
> I mean. It's hard to watch this new generation getting all excited about
> a program that, in the 1960s, wouldn't have merited mention on the nightly
> news.
>
> But I suppose that's all they really have to get excited about nowadays,
> with the space program completely shut down.
>
> NASA has sunk so far since I was a boy...it is to weep.
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"

It typical NASA hype. Note that they claimed to have "invented" virtually
everything new in the '60s.

Mike
MU-2

[Jay Masino]

Jay Honeck > wrote:
> On a deeper level, I find the enthusiasm about this scramjet flight to be,
> in many ways, pathetic.
>
> I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
> flight here -- which is somehow trumped up to be some sort of a huge success
> for NASA? Worse, they're claming that they've "beaten the speed record set
> by the X-15 some 40 years ago..."


The excitement is about the technology. I think the press is making a
bigger thing about the "record" than NASA really cares about. The ability
to run a jet engine, at close to Mach 10, without bringing along an
oxygen tank, is the REAL achievement. There will undoubtedly be many
more unmanned test flights before a manned flight is attempted with this
engine.

--- Jay



--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

[Don French]

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 :)

[Peter Duniho]

"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

[Chris W]

Jay Honeck wrote:

>On a deeper level, I find the enthusiasm about this scramjet flight to be,
>in many ways, pathetic.
>
>I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
>flight here -- which is somehow trumped up to be some sort of a huge success
>for NASA? Worse, they're claming that they've "beaten the speed record set
>by the X-15 some 40 years ago..."
>
>
I have to agree, I think this is really only a notch or 2 above a wind
tunnel experiment that went well.

--
Chris W

Gift Giving Made Easy
Get the gifts you want & give the
gifts they want this holiday season
http://thewishzone.com

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

[mhquay]

Mike Rapoport wrote:
> *"Jay Honeck" > wrote in message
> news:03Umd.45151$V41.23702@attbi_s52...
> >> 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.
> >
> > On a deeper level, I find the enthusiasm about this scramjet flight
> to be,
> > in many ways, pathetic.
> >
> > I mean, c'mon -- we're talking about an unmanned, rocket-assisted,
> 10
> > second flight here -- which is somehow trumped up to be some sort
> of a
> > huge success for NASA? Worse, they're claming that they've "beaten
> the
> > speed record set by the X-15 some 40 years ago..."
> >
> > Compare this sad little program to the heady days of the manned
> X-15, with
> > dozens of suborbital flights over a period of years, and you soon
> see what
> > I mean. It's hard to watch this new generation getting all excited
> about
> > a program that, in the 1960s, wouldn't have merited mention on the
> nightly
> > news.
> >
> > But I suppose that's all they really have to get excited about
> nowadays,
> > with the space program completely shut down.
> >
> > NASA has sunk so far since I was a boy...it is to weep.
> > --
> > Jay Honeck
> > Iowa City, IA
> > Pathfinder N56993
> > www.AlexisParkInn.com
> > "Your Aviation Destination"
>
> It typical NASA hype. Note that they claimed to have "invented"
> virtually
> everything new in the '60s.
>
> Mike
> MU-2 *

Well they didn't invent this one.
The scramjet was invented by Australian space engineer Professor Ray
Stalker.

Phil


--
mhquay
------------------------------------------------------------------------
Posted via OziPilots Online [ http://www.OziPilotsOnline.com.au ]
- A website for Australian Pilots regardless of when, why, or what they fly -

[JF]

> It typical NASA hype. Note that they claimed to have "invented" virtually
> everything new in the '60s.
>
> Mike
> MU-2

Well, NASA may not have "invented" everything new in the 60's, but they most
definitely paid for it ;)

[Morgans]

"Chris W" > wrote

> I have to agree, I think this is really only a notch or 2 above a wind
> tunnel experiment that went well.
>
> --
> Chris W

Bingo! That is exactly what it is intended to be. We don't have wind
tunnels that can do Mach 9, or they would have done this test, and many
more, in the wind tunnel.

Point is, they have an engine that does function with internal supersonic
flow. Now they can think about scaling it up to make it useful.
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.797 / Virus Database: 541 - Release Date: 11/15/2004

[Morgans]

"mhquay" > wrote

>
> Well they didn't invent this one.
> The scramjet was invented by Australian space engineer Professor Ray
> Stalker.
>
> Phil

They did make a working, flying version.
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.797 / Virus Database: 541 - Release Date: 11/15/2004

[mhquay]

Morgans wrote:
> *"mhquay" > wrote
>
> >
> > Well they didn't invent this one.
> > The scramjet was invented by Australian space engineer Professor
> Ray
> > Stalker.
> >
> > Phil
>
> They did make a working, flying version.
> --
> Jim in NC
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.797 / Virus Database: 541 - Release Date: 11/15/2004 *

No argument from me. I was just adding a bit of info to the thread.

Phil


--
mhquay
------------------------------------------------------------------------
Posted via OziPilots Online [ http://www.OziPilotsOnline.com.au ]
- A website for Australian Pilots regardless of when, why, or what they fly -

[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, 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

[Peter Duniho]

"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

[Don French]

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

[gatt]

"Jay Masino" > wrote in message news:419c904b$0

> The excitement is about the technology. I think the press is making a
> bigger thing about the "record" than NASA really cares about. The ability
> to run a jet engine, at close to Mach 10, without bringing along an
> oxygen tank, is the REAL achievement.

Exactly. All they care about is the proof of concept, although I'd be
surprised if it hasn't already been done out there. (Kinda like Cassini.)

-c

[alexy]

(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
life<g>), 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.

[Peter Duniho]

"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

[[email protected]]

The significance of all this is that it is an air breathing engine -
not one (like a rocket for example) that also has to bring its
oxidizer along. Yes, it takes a lot of speed to get it in positive
thrust territory, but it accelerated beyond that point to an even
higher speed. The engine is very simple in its construction and has
no primary moving parts - other than a large fuel pump.

There are more than a few details though to be ironed out before Tokyo
will be an hour away...........

[Don French]

The X-prize is different. They did what was required to win the
prize, which was get someone into space and return. Well, maybe the
scramjet did what was required to set the world's speed record too,
but it fails to impress since it wasn't the jet's engine that got it
going that fast. The jet only contributed the last few pounds of
thrust required to defeat air friction to keep it going at that speed
and maybe a few more to accelerate a half Mach or so.

I did a calculation that makes some assumptions that may or may not be
completely accurate. I am neither an aeronautical engineer or a fluid
dynamics expert, but I still made a go at trying to compute how
difficult it was for the scramjet to accelerate from Mach 9.5 to Mach
10.

Newton's first law of motion tells us that a plane released from a
rocket at Mach 10 will, in the absence of air friction, continue at
that speed indefinitely (or until it encounters another object, like
the Earth), and never have to turn on its engines to do so. The
scramjet only has to have enough power to overcome what little air
friction there is at 100,000 feet to maintain its release speed. The
question is how much air friction is there at Mach 10 at 100,000 feet.

Since I don't know how to compute the actual frictional effects at
that speed and altitude, it occured to me that maybe I can at least
compute the ratio between overcoming friction at that speed and
altitude and at say, Mach 1 at 5000 feet. That would provide a way of
making a comparison that makes sense to me.

My first assumption is that for the same air density, the friction is
directly proportional to the speed of the aircraft. If that is true,
the scramjet has to exert 10 times as much thrust to overcome friction
than a jet flying at Mach 1 for the same air density.

But the scramjet is flying at 20 times the altitude of the other jet,
and the air density is much lower up there. My second assumption is
that air resistance is directly proportional to air pressure. If this
is true, I can compute the relative ease of overcoming the friction by
simply computing relative air pressures. Air pressure decreases with
the square of the distance from Earth. So the difference between the
air pressure at 5000 feet and 100,000 feet is 1/20 squared, or 1/400.
And since air pressure and air density are proportional, there is
1/400 times as much air per cubic centimeter at 100,000 feet than
there is at 5,000 feet.

So, if all my assumptions are correct, then it is about 40 (400/10)
times as easy to maintain Mach 10 at 100,000 feet as it is to maintain
Mach 1 at 5000 feet. My final assumption is that this also means that
it takes about 1/40 the thrust to accelate from Mach 9.5 to Mach 10 at
100,000 feet as it does to accelerate from Mach Mach 1.0 to Mach 1.5
at 5000 feet. And if that is true, then it is also true that it takes
exactly the same amount of thrust to go from Mach 9.5 to Mach 10 at
100,000 feet as it takes to go from Mach 1 to Mach 1 plus 1/40 of a
half Mach. 1/40 of a half Mach is about 10 miles an hour increase in
speed.

Therefore, according to my calculations, if the scramjet accelerated
from Mach 9.5 to Mach 10, it took about as much thrust as for a jet
flying at Mach 1 at 5000 feet to increase its speed by 10 miles per
hour.

Like I said, I am neither an aeronautical engineer nor a fluid
dynamics expert, so consider the source. If there is an aeronautical
engineer or a fluid dynamics expert out there who can point out the
errors in these calculations, please do. Just leave out the flames,
OK? At least I made an attempt at reasoning through the problem and
realize my limitations.


-- Don French




>
> > 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.
>
> Hmm. Would you say the same for Yeager and the X-1, it having been dropped
> from the belly of another aircraft, or is your particular question related
> just to the rocket?
>
> Would this same sort of criteria apply to the X-prize given that Space Ship
> One was given a lift to an intermediate altitide?
>
> Interesting.
> -c

[Gene Seibel]

"Jay Honeck" > wrote in message news:<03Umd.45151$V41.23702@attbi_s52>...
> > 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.
>
> On a deeper level, I find the enthusiasm about this scramjet flight to be,
> in many ways, pathetic.
>
> I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
> flight here -- which is somehow trumped up to be some sort of a huge success
> for NASA? Worse, they're claming that they've "beaten the speed record set
> by the X-15 some 40 years ago..."

Take it easy on the poor media. The election is over and they are
desperate for something to talk about. ;)
--
Gene Seibel
Space Ship One - http://pad39a.com/gene/ss1.html
Because I fly, I envy no one - except Mike Melvill.

[Robert Briggs]

Peter Duniho wrote:
> Don French wrote:

> > ... 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.

Peter, your grasp of the physics of the matter seems to be substantially
better than Don's (not that that is difficult), but I don't buy the bit
about "the scramjet [being] the *entire* source of the speed".

If that were *truly* the case, there would have been no rocket and not
thundering great bomber involved.

What the flight *does* demonstrate is that once *other means* have been
used to get the aeroplane to the scramjet's working speed range *then*
the scramjet can accelerate further and maintain Mach 10 while its fuel
lasts.

The flight is a *proof-of-concept* for something which would require at
least one non-scramjet engine type to make a self-contained system.

[Jose]

> My first assumption is that for the same air density, the friction is
> directly proportional to the speed of the aircraft.

Nope. To oversimplify, it goes as the cube at subsonic speeds. Once supersonic other terms enter the equation. So at Mach 10 the scramjet would
have to exert more than 1000 times the thrust as for Mach 1 at the same altitude. And a scramjet can't run from a standing stop.

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[alexy]

(Don French) wrote:

>The X-prize is different. They did what was required to win the
>prize, which was get someone into space and return. Well, maybe the
>scramjet did what was required to set the world's speed record too,
>but it fails to impress since it wasn't the jet's engine that got it
>going that fast. The jet only contributed the last few pounds of
>thrust required to defeat air friction to keep it going at that speed
>and maybe a few more to accelerate a half Mach or so.
>
>I did a calculation that makes some assumptions that may or may not be
>completely accurate. I am neither an aeronautical engineer or a fluid
>dynamics expert, but I still made a go at trying to compute how
>difficult it was for the scramjet to accelerate from Mach 9.5 to Mach
>10.
>
>Newton's first law of motion tells us that a plane released from a
>rocket at Mach 10 will, in the absence of air friction, continue at
>that speed indefinitely (or until it encounters another object, like
>the Earth), and never have to turn on its engines to do so. The
>scramjet only has to have enough power to overcome what little air
>friction there is at 100,000 feet to maintain its release speed. The
>question is how much air friction is there at Mach 10 at 100,000 feet.
>
>Since I don't know how to compute the actual frictional effects at
>that speed and altitude, it occured to me that maybe I can at least
>compute the ratio between overcoming friction at that speed and
>altitude and at say, Mach 1 at 5000 feet. That would provide a way of
>making a comparison that makes sense to me.
>
>My first assumption is that for the same air density, the friction is
>directly proportional to the speed of the aircraft.
Bad assumption. I think that drag is proportional to the square of
speed.

> If that is true,
>the scramjet has to exert 10 times as much thrust to overcome friction
>than a jet flying at Mach 1 for the same air density.
100 times if it is square.

>But the scramjet is flying at 20 times the altitude of the other jet,
>and the air density is much lower up there. My second assumption is
>that air resistance is directly proportional to air pressure.
Intuitively that "feels" right. But I don't trust my intuition on
things like this.

>If this
>is true, I can compute the relative ease of overcoming the friction by
>simply computing relative air pressures. Air pressure decreases with
>the square of the distance from Earth.
Another assumption I would question. Please tell me you do not believe
that the air in New Orleans at 22'MSL is 57,000 time more dense and
higher pressured than the air in Denver!!!!

> So the difference between the
>air pressure at 5000 feet and 100,000 feet is 1/20 squared, or 1/400.
>And since air pressure and air density are proportional, there is
>1/400 times as much air per cubic centimeter at 100,000 feet than
>there is at 5,000 feet.

>So, if all my assumptions are correct, then it is about 40 (400/10)
>times as easy to maintain Mach 10 at 100,000 feet as it is to maintain
>Mach 1 at 5000 feet.
Highly suspect assumptions, even with sound reasoning, lead to highly
suspect conclusions.

> My final assumption is that this also means that
>it takes about 1/40 the thrust to accelate from Mach 9.5 to Mach 10 at
>100,000 feet as it does to accelerate from Mach Mach 1.0 to Mach 1.5
>at 5000 feet. And if that is true, then it is also true that it takes
>exactly the same amount of thrust to go from Mach 9.5 to Mach 10 at
>100,000 feet as it takes to go from Mach 1 to Mach 1 plus 1/40 of a
>half Mach. 1/40 of a half Mach is about 10 miles an hour increase in
>speed.
And you were complaining about the demise of physics education? <g>

>Therefore, according to my calculations, if the scramjet accelerated
>from Mach 9.5 to Mach 10, it took about as much thrust as for a jet
>flying at Mach 1 at 5000 feet to increase its speed by 10 miles per
>hour.
>
>Like I said, I am neither an aeronautical engineer nor a fluid
>dynamics expert
Glad you pointed that out!

>, so consider the source. If there is an aeronautical
>engineer or a fluid dynamics expert out there who can point out the
>errors in these calculations, please do.
I'm neither.

> Just leave out the flames,
>OK? At least I made an attempt at reasoning through the problem and
>realize my limitations.

Okay. Sorry for the sarcasm that crept in. But hopefully you see where
the assumptions look suspect to this layman.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

[John Galban]

(Don French) wrote in message >...
> Seriously,
> they could have dropped a Piper cub off that rocket and it could have
> maintained Mach 9 for hundreds of miles.

I know you started that sentence with the word "seriously", but you
can't be serious. A Piper Cub would instantly disintegrate at Mach 9,
assuming you were somehow able to protect it from the blast of
(relatively thin) air while you accellerated to that speed. It
certainly doubt that even the pieces would "maintain" Mach 9 long
enough to travel hundreds of miles. I'm pretty sure that they would
travel hundreds of miles, though.

John Galban=====>N4BQ (PA28-180)

[Morgans]

"Todd Pattist" > wrote

> It takes a lot more than "a few pounds of thrust" to fly at
> Mach 10.
>
> The temperature of the leading edge of the tail was 2600
> degrees F on the Mach 7 flight. They rebuilt flight
> surfaces to get to 10.

Indeed. Air friction heating a tail surface to 2600 degrees, sounds like
LOTS more than "a few pounds of thrust" would be needed to overcome
friction.
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.797 / Virus Database: 541 - Release Date: 11/16/2004

[Journeyman]

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)

[Peter Duniho]

"Robert Briggs" > wrote in message
...
> [...]
> Peter, your grasp of the physics of the matter seems to be substantially
> better than Don's (not that that is difficult), but I don't buy the bit
> about "the scramjet [being] the *entire* source of the speed".
>
> If that were *truly* the case, there would have been no rocket and not
> thundering great bomber involved.

Todd's interpretation of my statement was exactly correct. This particular
scramjet had limited fuel available, and all scramjets have the limitation
that they only operate in supersonic flight. These limitations forced the
use of a bomber and support rocket. But the thrust generated *exceeded*
that provided by the rocket, which is why the scramjet was able to
accelerate after being released from the rocket.

Had the scramjet had that thrust available from 0 mph, and had it had enough
fuel for the flight, it would have just as easily accelerated to Mach 10
from 0 mph as it did from Mach 9.

> What the flight *does* demonstrate is that once *other means* have been
> used to get the aeroplane to the scramjet's working speed range *then*
> the scramjet can accelerate further and maintain Mach 10 while its fuel
> lasts.

Yes, it does demonstrate that. Having a functional scramjet is a pretty
huge accomplishment.

> The flight is a *proof-of-concept* for something which would require at
> least one non-scramjet engine type to make a self-contained system.

Yes, it has always been understood that a scramjet by itself is not very
useful, since it can't be used from a standing start. The shuttle is not
very useful without its booster rockets, but that doesn't take away from the
engineering accomplishments of the shuttle itself.

Pete

[Don French]

NASA's site prominently mentions the speed record and the technology
hardly at all. Read all about it:

http://www.nasa.gov/missions/research/x43-main.html

(Jay Masino) wrote in message >...
> Jay Honeck > wrote:
> > On a deeper level, I find the enthusiasm about this scramjet flight to be,
> > in many ways, pathetic.
> >
> > I mean, c'mon -- we're talking about an unmanned, rocket-assisted, 10 second
> > flight here -- which is somehow trumped up to be some sort of a huge success
> > for NASA? Worse, they're claming that they've "beaten the speed record set
> > by the X-15 some 40 years ago..."
>
>
> The excitement is about the technology. I think the press is making a
> bigger thing about the "record" than NASA really cares about. The ability
> to run a jet engine, at close to Mach 10, without bringing along an
> oxygen tank, is the REAL achievement. There will undoubtedly be many
> more unmanned test flights before a manned flight is attempted with this
> engine.
>
> --- Jay

[Peter Duniho]

"Don French" > wrote in message
om...
> NASA's site prominently mentions the speed record and the technology
> hardly at all. Read all about it:
>
> http://www.nasa.gov/missions/research/x43-main.html

Well, a) for an "air-breathing engine", Mach 10 *is* a pretty amazing speed
record to break, and b) I really don't get your interpretation of the web
page you've pointed us to.

They mention the speed here and there, but the press release announcing the
successful flight concentrates almost entirely on the technology, and
certainly the technology is not given short shrift compared to the speed
anywhere else that I can find on that site.

Maybe you could quote exact language on that site that illustrates your
interpretation? Please don't forget to explain how the language negates all
the other mentions of the technology.

Pete

[alexy]

Jose > wrote:

>> My first assumption is that for the same air density, the friction is
>> directly proportional to the speed of the aircraft.
>
>Nope. To oversimplify, it goes as the cube at subsonic speeds. Once supersonic other terms enter the equation. So at Mach 10 the scramjet would
>have to exert more than 1000 times the thrust as for Mach 1 at the same altitude. And a scramjet can't run from a standing stop.
>
>Jose
Jose, hopefully someone will correct me if I'm wrong, but the drag
(and the thrust needed to overcome it) increase with the square of
velocity. It is the power needed that increases with v^3.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

[Mike Rapoport]

> wrote in message
om...
> There are more than a few details though to be ironed out before Tokyo
> will be an hour away...........

Like waiting for a rippin' wind right down the runway to get the engine
started!

Mike
MU-2

[Mike Rapoport]

Are you sure that you are really not an aeronautical engineer? Are you a
high school graduate?

Mike
MU-2

"Don French" > wrote in message
om...
> The X-prize is different. They did what was required to win the
> prize, which was get someone into space and return. Well, maybe the
> scramjet did what was required to set the world's speed record too,
> but it fails to impress since it wasn't the jet's engine that got it
> going that fast. The jet only contributed the last few pounds of
> thrust required to defeat air friction to keep it going at that speed
> and maybe a few more to accelerate a half Mach or so.
>
> I did a calculation that makes some assumptions that may or may not be
> completely accurate. I am neither an aeronautical engineer or a fluid
> dynamics expert, but I still made a go at trying to compute how
> difficult it was for the scramjet to accelerate from Mach 9.5 to Mach
> 10.
>
> Newton's first law of motion tells us that a plane released from a
> rocket at Mach 10 will, in the absence of air friction, continue at
> that speed indefinitely (or until it encounters another object, like
> the Earth), and never have to turn on its engines to do so. The
> scramjet only has to have enough power to overcome what little air
> friction there is at 100,000 feet to maintain its release speed. The
> question is how much air friction is there at Mach 10 at 100,000 feet.
>
> Since I don't know how to compute the actual frictional effects at
> that speed and altitude, it occured to me that maybe I can at least
> compute the ratio between overcoming friction at that speed and
> altitude and at say, Mach 1 at 5000 feet. That would provide a way of
> making a comparison that makes sense to me.
>
> My first assumption is that for the same air density, the friction is
> directly proportional to the speed of the aircraft. If that is true,
> the scramjet has to exert 10 times as much thrust to overcome friction
> than a jet flying at Mach 1 for the same air density.
>
> But the scramjet is flying at 20 times the altitude of the other jet,
> and the air density is much lower up there. My second assumption is
> that air resistance is directly proportional to air pressure. If this
> is true, I can compute the relative ease of overcoming the friction by
> simply computing relative air pressures. Air pressure decreases with
> the square of the distance from Earth. So the difference between the
> air pressure at 5000 feet and 100,000 feet is 1/20 squared, or 1/400.
> And since air pressure and air density are proportional, there is
> 1/400 times as much air per cubic centimeter at 100,000 feet than
> there is at 5,000 feet.
>
> So, if all my assumptions are correct, then it is about 40 (400/10)
> times as easy to maintain Mach 10 at 100,000 feet as it is to maintain
> Mach 1 at 5000 feet. My final assumption is that this also means that
> it takes about 1/40 the thrust to accelate from Mach 9.5 to Mach 10 at
> 100,000 feet as it does to accelerate from Mach Mach 1.0 to Mach 1.5
> at 5000 feet. And if that is true, then it is also true that it takes
> exactly the same amount of thrust to go from Mach 9.5 to Mach 10 at
> 100,000 feet as it takes to go from Mach 1 to Mach 1 plus 1/40 of a
> half Mach. 1/40 of a half Mach is about 10 miles an hour increase in
> speed.
>
> Therefore, according to my calculations, if the scramjet accelerated
> from Mach 9.5 to Mach 10, it took about as much thrust as for a jet
> flying at Mach 1 at 5000 feet to increase its speed by 10 miles per
> hour.
>
> Like I said, I am neither an aeronautical engineer nor a fluid
> dynamics expert, so consider the source. If there is an aeronautical
> engineer or a fluid dynamics expert out there who can point out the
> errors in these calculations, please do. Just leave out the flames,
> OK? At least I made an attempt at reasoning through the problem and
> realize my limitations.
>
>
> -- Don French
>
>
>
>
>>
>> > 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.
>>
>> Hmm. Would you say the same for Yeager and the X-1, it having been
>> dropped
>> from the belly of another aircraft, or is your particular question
>> related
>> just to the rocket?
>>
>> Would this same sort of criteria apply to the X-prize given that Space
>> Ship
>> One was given a lift to an intermediate altitide?
>>
>> Interesting.
>> -c

[Jose]

> Jose, hopefully someone will correct me if I'm wrong, but the drag
> (and the thrust needed to overcome it) increase with the square of
> velocity. It is the power needed that increases with v^3.

Yep. Misread it. But still far from linear.

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[Don French]

>
> > 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

[Don French]

>
> > 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

[Peter Duniho]

"Don French" > wrote in message
om...
> The law of inertia has nothing to do with this? It has everything to
> do with it.

No, it doesn't. Inertia is a very tiny component of the overall physics
problem.

> [...]
> 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.

There IS something acting upon it. Air resistance, which is VERY
significant at that speed, even with the relatively low air density.

> 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.

So you DO understand that there is air friction. Amazing.

> 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.

We are not talking about a situation in a vacuum.

> I see part of the problem.

No, you don't.

> You, like many non-technical people, think
> that inertia is only something to overcome.

What an odd statement. Inertia is simply inertia. It's not defined by what
one does to it.

> Inertia is as much about
> the difficulty in slowing something down as it speeding something up.

Is not speeding something up a matter of "overcoming inertia"?

> 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.

I don't have the exact density numbers in front of me, but you are certainly
mistaken about your method of calculating the air density at that altitude,
as well as your assumption as to just how significant drag is at that speed
and altitude.

> The frictionless scenario is the starting point for understanding the
> problem.

Unfortunately, you don't seem to be able to get past that starting point.

> 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.

I already understand that, and have been trying to point out all along that
the issue is "the power it takes to overcome friction". How nice of you to
finally show up at this party.

> [...] It makes
> the achievement of the scramjet more impressive than I thought.
> Thanks for educating me.

You are quite amusing. You spend the better part of a post insinuating that
I don't know my physics, and then bury a "mea culpa" in the middle,
admitting that all along you did not have your facts straight. That's rich.

> Well, I wasn't trying to personalize my statement

Of course you were...you started out accusing me of never having taken high
school physics. It doesn't get much more personal than that.

> and I don't think you really needed to either.

Needed to? No...probably not. Still, it seemed quite appropriate in
context (and still does).

> My statement is in fact true. Less and
> less people have a grasp of physics these days.

I don't dispute that claim. I think it's ironic coming from you though.

> 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.

And so? Are you trying to say that you should have known better? I'm a bit
lost as to what your point in describing your studies is.

Pete

[Neil Gould]

Hi all,
(this discussion is getting rather circular)

Recently, Don French > posted:
(largely snipped)

> [...] 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.
>
The problem, of course, is that scramjets don't operate in a vacuum.

> For what it is worth, there isn't a lot of air at 100,000 feet.
>
Then, what, exactly is the scramjet "breathing", and what, exactly, is
heating the leading edges of the surfaces to 2600°? Seems to be quite a
lot of air to me.

I really don't understand why aviators would rather diminish the
accomplishment than come to an understanding of it.

Neil

[alexy]

(Don French) wrote:

>>
>> > Look up Newton's first law of motion, the law of inertia.
>>
>> The law of inertia has nothing to do with this.
He probably should have more accurately said that the effect of
inertia is an insignificant factor in this. You are right that it has
something to do with it.
>
>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.
Which happens immediately due to the HUGE drag.

> 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.
Big "if"

> 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.
True. Not very relevant, but true.

>
>> > 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.
LOL! I think you are out of your depth in this discussion. And your
trying to paint others as "non-techincal" is laughable.

>
>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.

I don't know the amount, but yes, it is pretty thin. But drag is still
HUGE. Did you read Todd's post about how much it heated the tail
surfaces at Mach 7? That takes a huge amount of energy.
>
>>>
>> 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

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

[Mike Rapoport]

Don't you think that the air is "acting upon" the vehicle? Air resistance
is heating the vehicle to temperatures greater than those in a jet engine.

Mike
MU-2

"Don French" > wrote in message
om...
>>
>> > 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

[David CL Francis]

On Fri, 19 Nov 2004 at 22:53:26 in message
>, alexy >
wrote:
>Jose > wrote:
>
>>> My first assumption is that for the same air density, the friction is
>>> directly proportional to the speed of the aircraft.
>>
>>Nope. To oversimplify, it goes as the cube at subsonic speeds. Once
>>supersonic other terms enter the equation. So at Mach 10 the scramjet
>>would
>>have to exert more than 1000 times the thrust as for Mach 1 at the
>>same altitude. And a scramjet can't run from a standing stop.
>>
>>Jose
> Jose, hopefully someone will correct me if I'm wrong, but the drag
>(and the thrust needed to overcome it) increase with the square of
>velocity. It is the power needed that increases with v^3.

Perhaps it is time to insert the simple fundamental equation of
aerodynamic drag.

Drag = 0.5 * (air density)* ( a representative area - commonly wing
area )*(velocity squared)*( a 'constant that depends mostly on shape)

If using pounds divide the result by 'g': 32.2 ft/(second squared) for
an answer in pounds.

The speed of sound in air is proportional to the square root of the
absolute temperature of the air. Thus in the standard atmosphere the
speed of sound falls from 1,117 ft/sec at sea level to 968.5 ft sec at
36,000 ft. Above that it is constant up to around 80,000 ft when it
starts to rise again up to about 175,000 ft when it starts to fall
again!.

So the original simple calculation is wrong. It is more complex than I
have said as drag also depends on Mach number and a number called
Reynolds Number.

Altitude ft Speed of sound density
S.L. 1,117 ft/second 0.076475 lb/(cubic foot)
50,000 ft 968.5 ft/second 0.011642
100,000 ft 1003.2 ft/second 0.0010332

E&OE (' Errors And Omissions Excepted. That means I hope it's right but
I don't guarantee it! Check the tables yourself.)

I apologise that this is not metric units.
--
David CL Francis

[Jay Masino]

Peter Duniho > wrote:
> Well, a) for an "air-breathing engine", Mach 10 *is* a pretty amazing speed
> record to break, and b) I really don't get your interpretation of the web
> page you've pointed us to.
> They mention the speed here and there, but the press release announcing the
> successful flight concentrates almost entirely on the technology, and
> certainly the technology is not given short shrift compared to the speed
> anywhere else that I can find on that site.
> Maybe you could quote exact language on that site that illustrates your
> interpretation? Please don't forget to explain how the language negates all
> the other mentions of the technology.

In addition, these press releases are released by NASA public relations
people. The scientists and engineers working on the project are probably
more concerned with the advancement of the technology.

--- Jay


--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

[Robert Briggs]

Peter Duniho wrote:
> Robert Briggs wrote:
>
> > Peter, your grasp of the physics of the matter seems to be substantially
> > better than Don's (not that that is difficult), but I don't buy the bit
> > about "the scramjet [being] the *entire* source of the speed".

> Todd's interpretation of my statement was exactly correct. This particular
> scramjet had limited fuel available, and all scramjets have the limitation
> that they only operate in supersonic flight. These limitations forced the
> use of a bomber and support rocket. But the thrust generated *exceeded*
> that provided by the rocket, which is why the scramjet was able to
> accelerate after being released from the rocket.

Right.

> > The flight is a *proof-of-concept* for something which would require at
> > least one non-scramjet engine type to make a self-contained system.
>
> Yes, it has always been understood that a scramjet by itself is not very
> useful, since it can't be used from a standing start.

Agreed.

I simply think that your wording about "the scramjet [being] the
*entire* source of the speed", rather than its being "sufficiently
powerful to complete the acceleration to Mach 10" (or something to that
effect) is a tad loose.

[Peter Duniho]

"Robert Briggs" > wrote in message
...
> [...]
> I simply think that your wording about "the scramjet [being] the
> *entire* source of the speed", rather than its being "sufficiently
> powerful to complete the acceleration to Mach 10" (or something to that
> effect) is a tad loose.

It is the entire source of the speed. Had the scramjet not been operating
when it disconnected from the rocket, it would have quickly slowed to
subsonic speed and of course would eventually have come to a complete stop.
The speed of the rocket simply ensured proper operation of the scramjet
engine...in the end, it's contribution to the final speed of the scramjet
vehicle is irrelevant.

An engine sufficiently powerful to accelerate the test vehicle from Mach 9
to Mach 10 is sufficiently powerful to accelerate the test vehicle from 0
mph to Mach 10. There's nothing loose about that statement at all, and it's
perfectly correct. The rocket used to launch the scramjet has nothing to do
with how powerful the scramjet is, or its final speed. Only the scramjet
itself does.

Pete

[Kevin Darling]

"gatt" > wrote in message >...
> "Don French" > wrote in message
>
> > 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.
>
> Hmm. Would you say the same for Yeager and the X-1, it having been dropped
> from the belly of another aircraft, or is your particular question related
> just to the rocket?

In the same vein, many early airplanes needed a catapult to get up to
flying speed, including the Wrights' planes away from Kitty Hawk's
winds. Doesn't make them any less amazing.

Wikipedia makes an interesting point as well... that high-speed jets
taking off from an aircraft carrier need a catapult launcher to get
them up to flying speed. (Obviously the jets can also take off with a
long enough runway, but the similarity is that an assist to get to
speed shouldn't negate the accomplishment, in many people's opinions.)

Best, Kev

[Robert Briggs]

Peter Duniho wrote:
> Robert Briggs wrote:
>
> > I simply think that your wording about "the scramjet [being] the
> > *entire* source of the speed", rather than its being "sufficiently
> > powerful to complete the acceleration to Mach 10" (or something to
> > that effect) is a tad loose.
>
> It is the entire source of the speed.

I'm not convinced, but we seem to be disagreeing about semantics,
rather than about aeronautics.

> An engine sufficiently powerful to accelerate the test vehicle from
> Mach 9 to Mach 10 is sufficiently powerful to accelerate the test
> vehicle from 0 mph to Mach 10.

Sufficiently powerful to accelerate the test vehicle from 0 mph to
Mach 10, yes; actually capable of doing it, no because of the nature
of the beast.

> The rocket used to launch the scramjet has nothing to do with how
> powerful the scramjet is, or its final speed. Only the scramjet
> itself does.

The scramjet (with the aerodynamics and structural integrity of the
test vehicle) sets the *possible* final speed, but the bomber and
the rocket make an essential contribution to getting there.

[Robert Briggs]

Kevin Darling wrote:

> Wikipedia makes an interesting point as well... that high-speed jets
> taking off from an aircraft carrier need a catapult launcher to get
> them up to flying speed. (Obviously the jets can also take off with a
> long enough runway, but the similarity is that an assist to get to
> speed shouldn't negate the accomplishment, in many people's opinions.)

The assistance doesn't *negate* the accomplishment.

However, if the assistance is *necessary* then the accomplishment
is of something slightly different.

[Neil Gould]

Recently, Robert Briggs > posted:

> Kevin Darling wrote:
>
>> Wikipedia makes an interesting point as well... that high-speed jets
>> taking off from an aircraft carrier need a catapult launcher to get
>> them up to flying speed. (Obviously the jets can also take off with
>> a long enough runway, but the similarity is that an assist to get to
>> speed shouldn't negate the accomplishment, in many people's
>> opinions.)
>
> The assistance doesn't *negate* the accomplishment.
>
> However, if the assistance is *necessary* then the accomplishment
> is of something slightly different.
>
Perhaps the question at hand is the nature of the accomplishment; as I see
it, the accomplishment is getting a scramjet to work in the real world.
That is pretty amazing, IMO. Another accomplishment is that the _jet_ was
operating at Mach 10; equally amazing, as no other jet can do so, AFAIK.
The launch method would seem to be pretty much irrelevant to those
accomplishments.

Regards,

Neil

[Blueskies]

"Todd Pattist" > wrote in message ...
> (Don French) wrote:
>
<snip>>
> The temperature of the leading edge of the tail was 2600
> degrees F on the Mach 7 flight. They rebuilt flight
> surfaces to get to 10.
>
>
> "It is possible to fly without motors, but not without knowledge and skill."
> Wilbur Wright



Rebuilt what flight surfaces?

[Blueskies]

"Todd Pattist" > wrote in message ...
> "Blueskies" > wrote:
>
>>Rebuilt what flight surfaces?
>
> They partially rebuilt the fins and added a carbon-carbon
> composite material to the leading edges of the fins, nose
> and wings to handle the higher temperatures. Heating was
> expected to double over the Mach 7 flight.
>
> "It is possible to fly without motors, but not without knowledge and skill."
> Wilbur Wright

I thought you were saying that they rebuilt the mach 7 plane, which of course was lost in the ocean. I guess you are
saying that they rebuilt the mach 10 airframe before the flight to better handle the temps...