There was an article in the 9 May issue of Science regarding
air-breathing hypersonic engines (hypersonic = above Mach 5).
Apparently, an Australian group got one of these to work for the first
time and the Pentagon is seriously thinking about a major program to,
incrementally, reach Mach 12 by 2012. They want to deliver weapons
world wide in very short time spans.

This is a big deal because rockets need to carry their oxydizer and
this adds a lot of weight. If you can get oxygen from the atmosphere
-- a big problem because of oxygen atoms pass through the engine very
quickly making combustion difficult -- there is a huge weight decrease.

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect
and deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Al Globus wrote:

>There was an article in the 9 May issue of Science regarding
>air-breathing hypersonic engines (hypersonic = above Mach 5).
>Apparently, an Australian group got one of these to work for the first
>time and the Pentagon is seriously thinking about a major program to,
>incrementally, reach Mach 12 by 2012. They want to deliver weapons
>world wide in very short time spans.
>
>This is a big deal because rockets need to carry their oxydizer and
>this adds a lot of weight. If you can get oxygen from the atmosphere
>-- a big problem because of oxygen atoms pass through the engine very
>quickly making combustion difficult -- there is a huge weight decrease.
>
It's not nearly as simple as that though- the thrust to weight ratio of
scramjets is a lot less than a rocket (rockets often manage 100:1 or
better, scramjets would be lucky to get 20:1, and are less fuel
efficient and heavier due to having hypersonic air intakes), and
carrying the oxidiser with you isn't as bad as it sounds- the oxidiser
is almost free (pennies per kilogram for LOX for example), and the tanks
aren't much more expensive.

And when you realise that you're trading cheap oxidiser for expensive
metal it all starts to look a bit silly (especially for a weapons
system, where presumably you aren't able to reuse the scramjet).

--

-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
> It's not nearly as simple as that though- the thrust to weight
ratio of
> scramjets is a lot less than a rocket (rockets often manage 100:1
or
> better, scramjets would be lucky to get 20:1,

Is this because of physical laws or is scramjet technology immature
compared to rockets? Can more efficiency be squeezed from scramjets?

> and are less fuel efficient

Why?

and heavier due to having hypersonic air intakes)

Doesn't the lack of oxidizer compensate?

, and
> carrying the oxidiser with you isn't as bad as it sounds- the
oxidiser
> is almost free (pennies per kilogram for LOX for example), and the
tanks
> aren't much more expensive.

But the rocket equation limits the payload as a function of the ISP
and the mass of the fuel and oxidizer.

My understanding of the scramjet's appeal was that by not having to
carry the oxidizer onboard, the rocket equation would allow a larger
proportion as payload. Is this incorrect?

I never thought that the appeal was about saving the cost of the
oxidizer.

TangoMan

victoriatangoman wrote:

>--- In spacesettlers@yahoogroups.com, Ian Woollard
> wrote:
>
>>It's not nearly as simple as that though- the thrust to weight
>>
>>
>ratio of
>
>>scramjets is a lot less than a rocket (rockets often manage 100:1
>>
>>
>or
>
>>better, scramjets would be lucky to get 20:1,
>>
>>
>
>Is this because of physical laws or is scramjet technology immature
>compared to rockets?
>
You need an air intake. Air is not particularly dense (1kg/m^3). The air
intake is fairly heavy.

> Can more efficiency be squeezed from scramjets?
>
>>and are less fuel efficient
>>
>>
>
>Why?
>
The whole time you are in the atmosphere you are facing drag. Scramjets
work at about mach 6; and drag is a square law. Rockets leave the
atmosphere as soon as possible for this reason. The fuel is the only
thing that contains energy, and the scramjet is wasting lots of energy
in drag. Rockets waste some energy carrying the oxidiser around too, but
factors of a few at most. When you go through the equations, the
scramjet has used a bit more fuel, but carries little or no oxidiser
with it. Still, fuel costs are low with either approach.

>and heavier due to having hypersonic air intakes)
>
>Doesn't the lack of oxidizer compensate?
>
Gross Liftoff Weight of scramjet is much lower, but the dry weight of
the rocket is lower.

>, and
>
>>carrying the oxidiser with you isn't as bad as it sounds- the
>>
>>
>oxidiser
>
>>is almost free (pennies per kilogram for LOX for example), and the
>>
>>
>tanks
>
>>aren't much more expensive.
>>
>>
>
>But the rocket equation limits the payload as a function of the ISP
>and the mass of the fuel and oxidizer.
>
That doesn't directly link to price though.

>My understanding of the scramjet's appeal was that by not having to
>carry the oxidizer onboard, the rocket equation would allow a larger
>proportion as payload. Is this incorrect?
>
Maybe. Maybe not. It's not at all clear. The engines are much heavier,
and you need more fuel. And the vehicle needs extra cooling to avoid
vapourising at mach 6.

>I never thought that the appeal was about saving the cost of the
>oxidizer.
>
>TangoMan
>

--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

On Monday, May 19, 2003, at 09:07 PM, Ian Woollard wrote:

> It's not nearly as simple as that though- the thrust to weight ratio of
> scramjets is a lot less than a rocket (rockets often manage 100:1 or
> better, scramjets would be lucky to get 20:1,

Is this dry weight thrust to weight? Most rockets have only a few
percent payload because they have to lift all the fuel, and all the
fuel to lift that fuel, and so on.

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect
and deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

On Monday, May 19, 2003, at 10:08 PM, Ian Woollard wrote:

> And the vehicle (scram jet) needs extra cooling to avoid
> vapourising at mach 6.
>

If the vehicle is reusable, you need this protection anyway to get back
through the atmosphere.

The International Space Station (ISS) most important legacy may be
jump-starting space tourism. Consider: the first space tourist, Dennis
Tito, was supposed to go to the Soviet era Mir space station. Under
pressure from NASA, Russia de-orbited the Mir which resulted in Mr.
Tito going to the ISS instead. Now the Mir was old, smelly, crowded and
probably not all that nice. The ISS was brand new, shinny, much more
roomy, etc. Mr. Tito came back to Earth with glowing accounts of how
great space is. Would his experience have been as good on Mir?

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Al Globus wrote:

>On Monday, May 19, 2003, at 10:08 PM, Ian Woollard wrote:
>
>> And the vehicle (scram jet) needs extra cooling to avoid
>>vapourising at mach 6.
>>
>>
>If the vehicle is reusable, you need this protection anyway to get back
>through the atmosphere.
>
No, in fact you don't; not to the same degree at all. To exaggerate it
only a little it's like the difference between waving your hand through
a flame and holding your hand there for 15 minutes.

Atleast one project tried to develop a mach 6 hypersonic aeroplane and
tried to work out a way of avoiding it melting away- it turned out they
didn't know how to do that. The X15 managed it- but that did it by
leaving the atmosphere; you can't do that with a scramjet.

>Al Globus
>
--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

Al Globus wrote:

>On Monday, May 19, 2003, at 09:07 PM, Ian Woollard wrote:
>
>>It's not nearly as simple as that though- the thrust to weight ratio of
>>scramjets is a lot less than a rocket (rockets often manage 100:1 or
>>better, scramjets would be lucky to get 20:1,
>>
>>
>
>Is this dry weight thrust to weight?
>
Yes. The weight of the engine alone (although including the turbopumps),
no tanks or payload or anything, compared to its thrust. Jets mostly get
more like 5:1. A 15:1 jet would be big news.

The NK-39 achieves 130:1 (uses Kero). The Shuttle only manages 70:1,
(uses hydrogen)

> Most rockets have only a few
>percent payload because they have to lift all the fuel, and all the
>fuel to lift that fuel, and so on.
>
Yes about 1% payload is fairly typical. That doesn't directly push the
costs up though; fuel is the cheap bit. It's the armies of people that
are needed (or atleast used) to launch the vehicle that cost the money.

>---------------------
>The dinosaurs were destroyed by an asteroid because they weren't
>space-faring. It's almost as if Gaia then thought "Well, dinosaurs
>worked pretty well, but space-faring is necessary. Maybe I'll should
>try mammals this time." Humanity is now developing systems to detect
>and deflect asteroids, and could build orbital space colonies to spread
>beyond Earth to insure life would survive a planetary catastrophe.
>
>Al Globus
>CSC at NASA Ames Research Center
>http://www.nas.nasa.gov/~globus/home.html
>
>Views expressed in this email are only my opinions and are not the
>position of any organization I'm familiar with.
>

--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

On Friday, May 23, 2003, at 08:47 PM, Ian Woollard wrote:

>>
>> Is this dry weight thrust to weight?
>>
> Yes. The weight of the engine alone (although including the
> turbopumps),
> no tanks or payload or anything, compared to its thrust. Jets mostly
> get
> more like 5:1. A 15:1 jet would be big news.
>
> The NK-39 achieves 130:1 (uses Kero). The Shuttle only manages 70:1,
> (uses hydrogen)
>

Using dry weight to thrust ignores the main advantage of a scramjet --
it doesn't carry the oxydizer. A more meaningful measure is wet weight
to thrust.

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect
and deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

On Friday, May 23, 2003, at 08:47 PM, Ian Woollard wrote:

>> Most rockets have only a few
>> percent payload because they have to lift all the fuel, and all the
>> fuel to lift that fuel, and so on.
>>
>>
> Yes about 1% payload is fairly typical. That doesn't directly push the
> costs up though; fuel is the cheap bit. It's the armies of people that
> are needed (or atleast used) to launch the vehicle that cost the money.
>

While the fuel is not particularly expensive, it needs large tanks to
hold it, pumping systems to move it, insulation on the external tank to
fall off and put holes in wings. The extra weight puts additional
structural loads during launch. It's explosive nature requires all
kinds of safety measures. Etc.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Al Globus wrote,

"... insulation on the external tank to
fall off and put holes in wings. ..."

A lot of ice fell off the Saturn V during launch, but there were no wings
upon which that ice could fall. That ice falling off the external tank
caused damage to the Shuttle's leading edge should not be seen as an
indictment of rockets in general, but rather of the specific design of the
STS.

Ron
******

Al Globus
05/27/03 11:55 AM
Please respond to spacesettlers

To: spacesettlers@yahoogroups.com
cc:
Subject: Re: [spacesettlers] Air-breathing hypersonic engines

On Friday, May 23, 2003, at 08:47 PM, Ian Woollard wrote:

>> Most rockets have only a few
>> percent payload because they have to lift all the fuel, and all the
>> fuel to lift that fuel, and so on.
>>
>>
> Yes about 1% payload is fairly typical. That doesn't directly push the
> costs up though; fuel is the cheap bit. It's the armies of people that
> are needed (or atleast used) to launch the vehicle that cost the money.
>

While the fuel is not particularly expensive, it needs large tanks to
hold it, pumping systems to move it, insulation on the external tank to
fall off and put holes in wings. The extra weight puts additional
structural loads during launch. It's explosive nature requires all
kinds of safety measures. Etc.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

On Tuesday, May 27, 2003, at 09:41 AM, rmenich@... wrote:

> Al Globus wrote,
>
> "... insulation on the external tank to
> fall off and put holes in wings. ..."
>
> A lot of ice fell off the Saturn V during launch, but there were no
> wings
> upon which that ice could fall. That ice falling off the external
> tank
> caused damage to the Shuttle's leading edge should not be seen as an
> indictment of rockets in general, but rather of the specific design of
> the
> STS.
>

The point is that using a scramjet to eliminating the enormous amount
of oxydizer required for a rocket eliminates all kinds of complexity
and problems, some of which are not at all obvious.

>
> Al Globus
> 05/27/03 11:55 AM
> Please respond to spacesettlers
>
> To: spacesettlers@yahoogroups.com
> cc:
> Subject: Re: [spacesettlers] Air-breathing hypersonic
> engines
>
> On Friday, May 23, 2003, at 08:47 PM, Ian Woollard wrote:
>
>>> Most rockets have only a few
>>> percent payload because they have to lift all the fuel, and all the
>>> fuel to lift that fuel, and so on.
>>>
>>>
>> Yes about 1% payload is fairly typical. That doesn't directly push the
>> costs up though; fuel is the cheap bit. It's the armies of people that
>> are needed (or atleast used) to launch the vehicle that cost the
>> money.
>>
>
> While the fuel is not particularly expensive, it needs large tanks to
> hold it, pumping systems to move it, insulation on the external tank to
> fall off and put holes in wings. The extra weight puts additional
> structural loads during launch. It's explosive nature requires all
> kinds of safety measures. Etc.
>
> The materials in one asteroid (the largest ) are sufficient to make
> orbital space colonies with ~500 times the surface area of the Earth in
> usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
> for details.
>
> Al Globus
> CSC at NASA Ames Research Center
> http://www.nas.nasa.gov/~globus/home.html
>
> Views expressed in this email are only my opinions and are not the
> position of any organization I'm familiar with.
>
> Questions.
>
The International Space Station (ISS) most important legacy may be
jump-starting space tourism. Consider: the first space tourist, Dennis
Tito, was supposed to go to the Soviet era Mir space station. Under
pressure from NASA, Russia de-orbited the Mir which resulted in Mr.
Tito going to the ISS instead. Now the Mir was old, smelly, crowded and
probably not all that nice. The ISS was brand new, shinny, much more
roomy, etc. Mr. Tito came back to Earth with glowing accounts of how
great space is. Would his experience have been as good on Mir?

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Al Globus wrote,

"
The point is that using a scramjet to eliminating the enormous amount
of oxydizer required for a rocket eliminates all kinds of complexity
and problems, some of which are not at all obvious.
"

I'll grant you that. But we have 50+ years of experience with those
complexities, and we understand them quite well. Hypersonic propulsion
introduces a whole new set of complexities --- for example, management of
atmospheric heating of the airframe during extended high velocity flight
within the atmosphere --- with which we have very little experience. Do
you prefer the devil whom you don't know to the devil whom you do know?

Ron
******

On Tuesday, May 27, 2003, at 10:31 AM, rmenich@... wrote:

> Al Globus wrote,
>
> "
> The point is that using a scramjet to eliminating the enormous amount
> of oxydizer required for a rocket eliminates all kinds of complexity
> and problems, some of which are not at all obvious.
> "
>
> I'll grant you that. But we have 50+ years of experience with those
> complexities, and we understand them quite well. Hypersonic
> propulsion
> introduces a whole new set of complexities --- for example, management
> of
> atmospheric heating of the airframe during extended high velocity
> flight
> within the atmosphere --- with which we have very little experience.
> Do
> you prefer the devil whom you don't know to the devil whom you do know?

The devil we know costs too much and is too unreliable -- in dozens of
implementations. We needs something different and better. Scramjets
have a fundamental advantage -- they don't carry the oxydizer -- along
with disadvantages. Presently, research dollars for scramjets are
miniscule. Perhaps there are ways around the disadantages and, if so,
we need to find them.

>
> Ron
> ******
>
> Questions.
>
The International Space Station (ISS) most important legacy may be
jump-starting space tourism. Consider: the first space tourist, Dennis
Tito, was supposed to go to the Soviet era Mir space station. Under
pressure from NASA, Russia de-orbited the Mir which resulted in Mr.
Tito going to the ISS instead. Now the Mir was old, smelly, crowded and
probably not all that nice. The ISS was brand new, shinny, much more
roomy, etc. Mr. Tito came back to Earth with glowing accounts of how
great space is. Would his experience have been as good on Mir?

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Al Globus wrote:

>Using dry weight to thrust ignores the main advantage of a scramjet --
>it doesn't carry the oxydizer.
>
It does if it wants to get to orbit- you can't just fly out of the
atmosphere straight into orbit. Also, note that all the practical
scramjets use liquid hydrogen for their fuel; so you still have deeply
cryogenic fuel for the vehicle.

> A more meaningful measure is wet weight
>to thrust.
>
Not in isolation. It's not about metrics, it's about systems. Americans
tried to build something like this 15 years ago, they failed. Hypersonic
aeroplanes have been a research topic for about 30+ years; and doesn't
appear to have made very much progress. The most successful hypersonic
vehicle is the Shuttle, and by a very long way (unless there is some
black project that nobody is talking about.)

>Al Globus
>CSC at NASA Ames Research Center
>http://www.nas.nasa.gov/~globus/home.html
>
--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

Al Globus wrote:

>While the fuel is not particularly expensive, it needs large tanks to
>hold it,
>
Only somewhat. The Shuttle's especially huge tank is because it uses
liquid hydrogen. But liquid hydrogen has appalling low density. LOX and
Kero is much, much denser. Exhaust velocity isn't so high, so you need 2
stages. But then again- the Shuttle uses multiple stages anyway, so why
use liquid hydrogen? And kerosene is much cheaper to handle and to buy,
and about 17 times denser than LH. Oh yeah, BTW that's a problem with
scramjets- the tanks are really, really huge with pure LH, (the LOX
brings up the average density of the Shuttles propellent tank), and
scramjets use more liquid hydrogen than the Shuttle does anyway.

> pumping systems to move it,
>
You don't always require pumps in fact. Just having tanks pressurised
above the combustion chamber pressure works, but is heavy. There's also
been some recent advances in this area- www.flometrics.com have a new,
simple, cheap pump with the same power/weight ratio as turbopumps. Still
undergoing development, but looks very promising indeed.

> insulation on the external tank to fall off and put holes in wings.
>
That was a total fuck-up in the Shuttle design. I'm not at all happy
with the idea of wings on space vehicles. I think they are unnecessary;
and sticking them underneath a huge cryotank- don't do that. Still, I
think probably NASA will solve the insulation issues well enough, but
possibly not completely. But the Shuttle architecture is pretty poor
IMHO- I generally prefer VTVL designs (Yay DC-X!) I think they are
potentially more reliable.

> The extra weight puts additional structural loads during launch.
>
Doesn't seem too bad a problem. Structural failures are fairly rare in
practice.

> It's explosive nature requires all kinds of safety measures. Etc.
>
Yes. That's true. Liquid oxygen supports combustion of even the metal
parts of the vehicle. Still, it is usually pretty difficult to trigger
combustion- the metal has to reach far over a 1500C to burn. Having
oxygen onboard usually exacerbates minor problems with the vehicle further.

Even hydrogen can explode in the absence of any oxidiser. Liquid
hydrogen expands enormously upon heating and then any pressure vessels
will burst; and you need cryogenic fuel for scramjets.

I'm currently working on a two stage launcher. I think about $1000/kg
(price) is achieveable, with decent profit margins. That corresponds to
a space tourism price of about $200,000 per person. I also think it will
be more reliable than the Shuttle. But I hope to see.

>Al Globus
>CSC at NASA Ames Research Center
>http://www.nas.nasa.gov/~globus/home.html
>
--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
> Al Globus wrote:
>
> >Using dry weight to thrust ignores the main advantage of a
scramjet --
> >it doesn't carry the oxydizer.
> >
> It does if it wants to get to orbit- you can't just fly out of the
> atmosphere straight into orbit. Also, note that all the practical
> scramjets use liquid hydrogen for their fuel; so you still have
deeply
> cryogenic fuel for the vehicle.
>
> > A more meaningful measure is wet weight
> >to thrust.
> >
> Not in isolation. It's not about metrics, it's about systems.

I'm following this debate with interest and am considering both
sides of the question, but your comment above doesn't elaborate
enough for me to even understand what the heck you mean. Would you
please elaborate.

TangoMan

victoriatangoman wrote:

>--- In spacesettlers@yahoogroups.com, Ian Woollard
> wrote:
>
>>Al Globus wrote:
>>
>>
>>
>>>Using dry weight to thrust ignores the main advantage of a
>>>
>>>
>scramjet --
>
>>>it doesn't carry the oxydizer.
>>>
>>>
>>>
>>It does if it wants to get to orbit- you can't just fly out of the
>>atmosphere straight into orbit. Also, note that all the practical
>>scramjets use liquid hydrogen for their fuel; so you still have
>>
>>
>deeply
>
>>cryogenic fuel for the vehicle.
>>
>>> A more meaningful measure is wet weight
>>>to thrust.
>>>
>>>
>>>
>>>
>>Not in isolation. It's not about metrics, it's about systems.
>>
>>
>I'm following this debate with interest and am considering both
>sides of the question, but your comment above doesn't elaborate
>enough for me to even understand what the heck you mean. Would you
>please elaborate.
>
Well, actually, rockets wet weight to thrust ratio is almost unlimited
anyway. The dry thrust:weight of a rocket engine is 100:1. Normally a
multistage launch vehicle has only about 1.5:1 overall thrust to weight
ratio (most of which is fuel, and only about 1.5 % is engine). But
there's no particular reason you can't add extra engines in- you end up
with less payload, but the thrust:wet weight has gone up. SSTO optimises
at about 3:1 thrust:weight anyway for various reasons.

Scramjets seem to be mostly interesting to the military- they want to go
places really quickly, outrace all the missiles etc. etc. But getting to
orbit? It might make a good first stage, but you're still going to need
rockets either in the first stage (in which case the scramjet has added
quite a bit to your first stage's orbital weight), or as a second (in
which case you've spent lots of money to create a not very special first
stage).

I guess the main metrics that matter are: payload size, cost/kg,
demonstrated reliability, launch rate. That's what I mean by systems,
it's about multiple metrics simultaneously.

>TangoMan
>
--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?

On Tuesday, May 27, 2003, at 03:45 PM, Ian Woollard wrote:

> Scramjets seem to be mostly interesting to the military- they want to
> go
> places really quickly, outrace all the missiles etc. etc. But getting
> to
> orbit? It might make a good first stage, but you're still going to need
> rockets either in the first stage (in which case the scramjet has added
> quite a bit to your first stage's orbital weight), or as a second (in
> which case you've spent lots of money to create a not very special
> first
> stage).
>

Obviously a scramjet by itself can't get you to orbit, at the very
minimum you need a rocket for the circularization burn. However, by
radically reducing the wet weight of a first stage they could make a
major contribution. For example, if my a calculation I did a couple
years ago is correct, it's interesting to note that on the shuttle the
solids are there mostly to lift themselves and the oxygen.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

A scramjet would also need a first stage to get it up to a sufficient
speed at which the scramjet can 'start'. Ramjets and scramjets can't
just take off from a standing start on a runway. If you disagree, then
please provide a reference URL; thanks.

Thus, you'd need
1.) A first stage, to accelerate the package from a standing start to some
supersonic speed at which the scramjet could start.
2.) A second, scramjet stage, to accelerate the package from some
hopefully low starting Mach number to a high Mach number within the
atmosphere.
3.) A third rocket stage for the final push to orbit plus circularization.

There are already two-stage-to-orbit rockets such as Delta IV. Do you
think that a three-stage-to-orbit system with scramjet as the second stage
would be preferable to a two-stage-to-orbit vehicle?

Ron
******

Al Globus
05/29/03 11:55 AM
Please respond to spacesettlers

To: spacesettlers@yahoogroups.com
cc:
Subject: Re: [spacesettlers] Re: Air-breathing hypersonic engines

On Tuesday, May 27, 2003, at 03:45 PM, Ian Woollard wrote:

> Scramjets seem to be mostly interesting to the military- they want to
> go
> places really quickly, outrace all the missiles etc. etc. But getting
> to
> orbit? It might make a good first stage, but you're still going to need
> rockets either in the first stage (in which case the scramjet has added
> quite a bit to your first stage's orbital weight), or as a second (in
> which case you've spent lots of money to create a not very special
> first
> stage).
>

Obviously a scramjet by itself can't get you to orbit, at the very
minimum you need a rocket for the circularization burn. However, by
radically reducing the wet weight of a first stage they could make a
major contribution. For example, if my a calculation I did a couple
years ago is correct, it's interesting to note that on the shuttle the
solids are there mostly to lift themselves and the oxygen.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

There's at least one proposed craft on the internet that combines a
rocket-assisted turbofan from takeoff to Mach 2, a ramjet up to Mach 8, then
a scramjet from there to about Mach 15. This guy has worked out a lot of
the engineering. However this is still the first stage, and the point of
this amazing aircraft (in his scheme) is to bring a second stage close to a
skyhook hanging down into the upper atmosphere, attached to a Space
Elevator-like satellite in geosynch.

see
http://www.affordablespaceflight.com/nasa1.html

I'm not aerospace engineer, but I'm impressed with the amount of work he's
done in thrust, weight, fuel mixes and powerplant design.

>A scramjet would also need a first stage to get it up to a sufficient
>speed at which the scramjet can 'start'. Ramjets and scramjets can't
>just take off from a standing start on a runway. If you disagree, then
>please provide a reference URL; thanks.
>
>Thus, you'd need
>1.) A first stage, to accelerate the package from a standing start to some
>supersonic speed at which the scramjet could start.
>2.) A second, scramjet stage, to accelerate the package from some
>hopefully low starting Mach number to a high Mach number within the
>atmosphere.
>3.) A third rocket stage for the final push to orbit plus circularization.
>
>There are already two-stage-to-orbit rockets such as Delta IV. Do you
>think that a three-stage-to-orbit system with scramjet as the second stage
>would be preferable to a two-stage-to-orbit vehicle?
>
>Ron
>******
>
>Al Globus
>05/29/03 11:55 AM
>Please respond to spacesettlers
>
> To: spacesettlers@yahoogroups.com
> cc:
> Subject: Re: [spacesettlers] Re: Air-breathing hypersonic
>engines
>
>On Tuesday, May 27, 2003, at 03:45 PM, Ian Woollard wrote:
>
> > Scramjets seem to be mostly interesting to the military- they want to
> > go
> > places really quickly, outrace all the missiles etc. etc. But getting
> > to
> > orbit? It might make a good first stage, but you're still going to need
> > rockets either in the first stage (in which case the scramjet has added
> > quite a bit to your first stage's orbital weight), or as a second (in
> > which case you've spent lots of money to create a not very special
> > first
> > stage).
> >
>Obviously a scramjet by itself can't get you to orbit, at the very
>minimum you need a rocket for the circularization burn. However, by
>radically reducing the wet weight of a first stage they could make a
>major contribution. For example, if my a calculation I did a couple
>years ago is correct, it's interesting to note that on the shuttle the
>solids are there mostly to lift themselves and the oxygen.
>
>The materials in one asteroid (the largest ) are sufficient to make
>orbital space colonies with ~500 times the surface area of the Earth in
>usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
>for details.
>
>Al Globus
>CSC at NASA Ames Research Center
>http://www.nas.nasa.gov/~globus/home.html
>
>Views expressed in this email are only my opinions and are not the
>position of any organization I'm familiar with.
>

STOP MORE SPAM with the new MSN 8 and get 2 months FREE*

Picky, picky. The air turborocket and the ramjet/scramjet are not
separated into two separate stages in that concept; that is, the air
turborocket that accelerates from standstill to Mach 2.5 is not shed, but
rather is shut off and carried as deadweight from Mach 2.5 to Mach 14-18
by the ramjet/scramjet.

I shouldn't have used the word 'stage'. Let me rephrase my initial
statement substituting "propulsion system" for "stage":

"
Thus, you'd need
1.) A first propulsion system, to accelerate the package from a standing
start to some supersonic speed at which the scramjet could start.
2.) A second, ramjet/scramjet propulsion system, to accelerate the package
from some hopefully low starting Mach number to a high Mach number within
the atmosphere.
3.) A third propulsion system for the final push to orbit plus
circularization.
"

The point is that the vehicle still needs three separate propulsion
systems, with adjustable inlet and outlet doors, etc., and that's a heck
of a lot of complexity. By contrast, Delta IV has only two propulsion
systems. Complexity means that a lot of things can go wrong.

Ron
******

"Brad Walsh"
05/30/03 09:50 AM
Please respond to spacesettlers

To: spacesettlers@yahoogroups.com
cc:
Subject: Re: [spacesettlers] Re: Air-breathing hypersonic engines

There's at least one proposed craft on the internet that combines a
rocket-assisted turbofan from takeoff to Mach 2, a ramjet up to Mach 8,
then
a scramjet from there to about Mach 15. This guy has worked out a lot of
the engineering. However this is still the first stage, and the point of
this amazing aircraft (in his scheme) is to bring a second stage close to
a
skyhook hanging down into the upper atmosphere, attached to a Space
Elevator-like satellite in geosynch.

see
http://www.affordablespaceflight.com/nasa1.html

I'm not aerospace engineer, but I'm impressed with the amount of work he's

done in thrust, weight, fuel mixes and powerplant design.

>A scramjet would also need a first stage to get it up to a sufficient
>speed at which the scramjet can 'start'. Ramjets and scramjets can't
>just take off from a standing start on a runway. If you disagree, then
>please provide a reference URL; thanks.
>
>Thus, you'd need
>1.) A first stage, to accelerate the package from a standing start to
some
>supersonic speed at which the scramjet could start.
>2.) A second, scramjet stage, to accelerate the package from some
>hopefully low starting Mach number to a high Mach number within the
>atmosphere.
>3.) A third rocket stage for the final push to orbit plus
circularization.
>
>There are already two-stage-to-orbit rockets such as Delta IV. Do you
>think that a three-stage-to-orbit system with scramjet as the second
stage
>would be preferable to a two-stage-to-orbit vehicle?
>
>Ron
>******
>
>Al Globus
>05/29/03 11:55 AM
>Please respond to spacesettlers
>
> To: spacesettlers@yahoogroups.com
> cc:
> Subject: Re: [spacesettlers] Re: Air-breathing hypersonic

>engines
>
>On Tuesday, May 27, 2003, at 03:45 PM, Ian Woollard wrote:
>
> > Scramjets seem to be mostly interesting to the military- they want to
> > go
> > places really quickly, outrace all the missiles etc. etc. But getting
> > to
> > orbit? It might make a good first stage, but you're still going to
need
> > rockets either in the first stage (in which case the scramjet has
added

On Friday, May 30, 2003, at 05:25 AM, rmenich@... wrote:

> A scramjet would also need a first stage to get it up to a sufficient
> speed at which the scramjet can 'start'. Ramjets and scramjets can't
> just take off from a standing start on a runway. If you disagree,
> then
> please provide a reference URL; thanks.
>
> Thus, you'd need
> 1.) A first stage, to accelerate the package from a standing start to
> some
> supersonic speed at which the scramjet could start.
> 2.) A second, scramjet stage, to accelerate the package from some
> hopefully low starting Mach number to a high Mach number within the
> atmosphere.
> 3.) A third rocket stage for the final push to orbit plus
> circularization.
>
> There are already two-stage-to-orbit rockets such as Delta IV. Do you
> think that a three-stage-to-orbit system with scramjet as the second
> stage
> would be preferable to a two-stage-to-orbit vehicle?

This is straightforward engineering trade. Given the current state of
the art, obviously no. However, the scramjet eliminates so much weight
from the system it deserves some significant R&D, even if it ultimately
doesn't pan out. One thing we really want to avoid is pinning
everything on a single path (e.g., the shuttle in the 70s).

One way to handle the first stage is to use a more-or-less standard
airplane to drop the second/third stage from a high point. By going
down you (hopefully) get enough speed to start the scramjet and then
pull up.

You might even consider mid-air fueling of the scramjet after takeoff
to reduce takeoff weight. Clearly this is heading towards a lot of
operational complexity, but subsonic aircraft and even mid-air
refueling are well understood and relatively inexpensive technologies.

>
> Ron
> ******
>
> Al Globus
> 05/29/03 11:55 AM
> Please respond to spacesettlers
>
> To: spacesettlers@yahoogroups.com
> cc:
> Subject: Re: [spacesettlers] Re: Air-breathing
> hypersonic engines
>
> On Tuesday, May 27, 2003, at 03:45 PM, Ian Woollard wrote:
>
>> Scramjets seem to be mostly interesting to the military- they want to
>> go
>> places really quickly, outrace all the missiles etc. etc. But getting
>> to
>> orbit? It might make a good first stage, but you're still going to
>> need
>> rockets either in the first stage (in which case the scramjet has
>> added
>> quite a bit to your first stage's orbital weight), or as a second (in
>> which case you've spent lots of money to create a not very special
>> first
>> stage).
>>
>
> Obviously a scramjet by itself can't get you to orbit, at the very
> minimum you need a rocket for the circularization burn. However, by
> radically reducing the wet weight of a first stage they could make a
> major contribution. For example, if my a calculation I did a couple
> years ago is correct, it's interesting to note that on the shuttle the
> solids are there mostly to lift themselves and the oxygen.
>
> The materials in one asteroid (the largest ) are sufficient to make
> orbital space colonies with ~500 times the surface area of the Earth in
> usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
> for details.
>
> Al Globus
> CSC at NASA Ames Research Center
> http://www.nas.nasa.gov/~globus/home.html
>
> Views expressed in this email are only my opinions and are not the
> position of any organization I'm familiar with.
>
> Questions.
>

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect
and deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

On Friday, May 30, 2003, at 07:38 AM, rmenich@... wrote:

> The point is that the vehicle (scramjet) still needs three separate
> propulsion
> systems, with adjustable inlet and outlet doors, etc., and that's a
> heck
> of a lot of complexity. By contrast, Delta IV has only two
> propulsion
> systems.

Unfortunately, we know without question that the Delta IV is way too
expensive and unreliable to support large scale colonization. There
are lots of similar rockets with, to first order, the same problem so
it's not just the Delta IV implementation. Therefore, we need something
a lot better. A scramjet may or may not be part of that solution, but
it has enough potential (IMHO) enough to deserve significant R&D.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

Wow, give Delta 4 a chance. It's a new rocket with, I think, a perfect
record of 2-for-2 so far.

Ron
*******

Al Globus
05/30/03 11:53 AM
Please respond to spacesettlers

To: spacesettlers@yahoogroups.com
cc:
Subject: Re: [spacesettlers] Re: Air-breathing hypersonic engines

On Friday, May 30, 2003, at 07:38 AM, rmenich@... wrote:

> The point is that the vehicle (scramjet) still needs three separate
> propulsion
> systems, with adjustable inlet and outlet doors, etc., and that's a
> heck
> of a lot of complexity. By contrast, Delta IV has only two
> propulsion
> systems.

Unfortunately, we know without question that the Delta IV is way too
expensive and unreliable to support large scale colonization. There
are lots of similar rockets with, to first order, the same problem so
it's not just the Delta IV implementation. Therefore, we need something
a lot better. A scramjet may or may not be part of that solution, but
it has enough potential (IMHO) enough to deserve significant R&D.

The materials in one asteroid (the largest ) are sufficient to make
orbital space colonies with ~500 times the surface area of the Earth in
usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.

On Friday, May 30, 2003, at 09:09 AM, rmenich@... wrote:

> Wow, give Delta 4 a chance. It's a new rocket with, I think, a
> perfect
> record of 2-for-2 so far.

With regard to price, Delta costs about as much as many other rockets.
The number of launches is far too small to make any conclusions, but
Delta IV is much like many other rockets. Good numbers are hard to
come by, but according to data in a recent Space News the failure rate
of commercial rockets is about 7%.

>
> Ron
> *******
>
> Al Globus
> 05/30/03 11:53 AM
> Please respond to spacesettlers
>
> To: spacesettlers@yahoogroups.com
> cc:
> Subject: Re: [spacesettlers] Re: Air-breathing
> hypersonic engines
>
> On Friday, May 30, 2003, at 07:38 AM, rmenich@... wrote:
>
>> The point is that the vehicle (scramjet) still needs three separate
>> propulsion
>> systems, with adjustable inlet and outlet doors, etc., and that's a
>> heck
>> of a lot of complexity. By contrast, Delta IV has only two
>> propulsion
>> systems.
>
> Unfortunately, we know without question that the Delta IV is way too
> expensive and unreliable to support large scale colonization. There
> are lots of similar rockets with, to first order, the same problem so
> it's not just the Delta IV implementation. Therefore, we need something
> a lot better. A scramjet may or may not be part of that solution, but
> it has enough potential (IMHO) enough to deserve significant R&D.
>
> The materials in one asteroid (the largest ) are sufficient to make
> orbital space colonies with ~500 times the surface area of the Earth in
> usable real estate. See http://lifesci3.arc.nasa.gov/SpaceSettlement/
> for details.
>
> Al Globus
> CSC at NASA Ames Research Center
> http://www.nas.nasa.gov/~globus/home.html
>
> Views expressed in this email are only my opinions and are not the
> position of any organization I'm familiar with.
>
> Questions.
>

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect
and deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.