From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Tue, 04 Apr 2000 16:59:02 GMT

On Tue, 4 Apr 2000 14:22:45 GMT, in a place far, far away,
henry@spsystems.net (Henry Spencer) made the phosphor on my monitor
glow in such a way as to indicate that:


>Remember that RLVs produce sonic booms too, near their takeoff and landing
>sites.  That's not as bad as booming the entire route in between, but it's
>not a trivial problem either.

Yes, and it's much more difficult to get rid of the shock in an
accelerating vehicle than one that can be optimized for a cruise
condition.

>Also, there is some possibility of boomless supersonic aircraft, as Rand
>has already alluded to.  There's an interesting design concept which just
>might achieve it.  (It looked plausible to me, but I'm not an aerodynamics
>type and can't really give an informed professional opinion on it.  And
>no, alas, I can't describe the details -- Non Disclosure Agreement.)

I may be able to discuss them very soon (which means that you can
also)...


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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Tue, 04 Apr 2000 22:04:01 GMT

On 04 Apr 2000 17:26:10 -0400, in a place far, far away, Steinn
Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
glow in such a way as to indicate that:

>> Not publicly--though we have been distributing information on it to
>> interested parties (primarily investors) without proprietary stamp.
>
>So, don't tease!
>What is the idea, if it is circulating
>without DNA, then might as well let it out
>for a sanity check.

Oh, it's already had plenty of that, and it's not clear that this is
the best venue for it <g>.  Not that there aren't some very astute
assessors in this group.  Mainly because I don't want to take the time
to post a full explanation here.  But I'll provide a brief description
at the end of this post, which I'm sure will initiate a long-duration
dialogue on the subject to clarify it that I haven't time for.   :-)

>> >or did a friendly
>> >Congresscritter make NASA look at it?
>
>> That actually happened three years ago.  In fact, Congress
>> appropriated $2M to the High-Speed Research budget to have them issue
>> a contract to us to develop it further--they flatly refused.  NASA
>> decided they didn't like it, 'cause it made HSCT look like a dog.  A
>> moot point, now, of course...  :-)
>
>Or NASA didn't like it because they hate having
>things rammed down their throat and being made to
>spend money on speculative ideas like that
> - Congresscritters have a terrible record chasing
>after crackpot fads and pseudo-science and
>NASA has to put up with enough mandated that
>they can't refuse.

Yes, I'm sure that this was part of it, but they are pursuing even
wackier things on their own...

>Why not put the idea in for a normal proposal
>and get the money out of code R?

We submitted an unsolicited proposal to NASA (handed it directly to
Dan Goldin and Bob Whitehead) even before Congress appropriate the
money.  They circular filed it.  Later, after the funds were
appropriated, Ames wanted to manage the program with us as contractor,
and Langely told them that if they did, they could kiss goodbye to the
six million per annum that they were getting from them for CFD.  Draw
your own conclusions...

>(Yeah, I know there are reasons you might
>not want to, but if you didn't even try
>to put it through peer review, then it
>looks mighty suspicious).

As I said, NASA looked at it, and rejected it, with no substantive
critique or description of why it would not work, except that we got
the impression that they considered shock waves to be some sort of law
of nature.

OK, here's a brief summary.  Shock waves are nature's way of providing
a reaction to the wing circulation in supersonic flight.  In subsonic
flight (as Prandtl discovered) there is a bound vortex around the
wing, and an uplift of the air upstream to allow the downturn behind
to provide lift.  This can't happen in supersonic flight, because the
air up ahead doesn't know the airplane is coming.  So instead, shock
waves form off the leading edge, which interact with the expansion
fans to form vortex sheets.  The net sum of these sheets and the wing
circulation add up to zero to conserve angular momentum, but it's very
inefficient, because the vortex sheets are of both signs, and generate
a lot more momentum (absolute magnitude) than is required to simply
balance the circulation.  They result in a lot of heating of the air
in the wake (where most of the energy goes--the sonic boom is a tiny
percentage of it), which of course contributes not at all to moving
the airplane, hence the high fuel costs for supersonic flight.

We've solved the problem by creating an artificial reaction to the
circulation with an underwing air jet (using a small amount of bleed
air from the first stage of the compressor) that recaptures the
compression waves before they can coalesce into shock waves.  We're
fooling mother nature by introducing additional energy into the air
flow, and adding in the energy term in Crocco's equation that normally
gets zeroed out because of the assumption of constant speed and
altitude at cruise.  When you do this, you can eliminate the entropy
term...

Clear as mud?



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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Tue, 04 Apr 2000 22:40:37 GMT

On Tue, 04 Apr 2000 22:22:08 GMT, in a place far, far away,
jakemcguire@my-deja.com made the phosphor on my monitor glow in such a
way as to indicate that:

>> Do tell - I was quite intrigued when you
>> floated a teaser on this a few months ago
>>  - so is it published or did a friendly
>> Congresscritter make NASA look at it?
>
>  I'm guessing that it has more to do with the new DARPA "Quiet
>Supersonic Reece UAV" that has been recently talked about.

I don't know anything about that.  It's mainly due to the fact that
the patents are all in place, both here and internationally, and it
seems a better policy at this point to publicize it than to keep it
under wraps.  Also, Jerry Rising and one of his colleagues at LockMart
have filed a patent for a flying supersonic wing that cites our
patents.

>Anyway, I'm
>quite interested to hear more.  No money to invest (yet - heh) but
>interested none the less.

See my other post.


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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Wed, 05 Apr 2000 13:48:03 GMT

On Wed, 05 Apr 2000 09:33:52 GMT, in a place far, far away, Ian
Stirling <Inquisitor@I.am> made the phosphor on my monitor glow in
such a way as to indicate that:

>>Yes, and it's much more difficult to get rid of the shock in an
>>accelerating vehicle than one that can be optimized for a cruise
>>condition.
>
>Unless fuel costs are small anyway, and you can live with going
>up at just under mach 1, until you get high enough.

Well, the problem isn't the fuel costs per se, but building a vehicle
large enough to carry the necessary fuel, and still have payload left.

>(What is high enough?)

Pretty much out of the atmosphere (I'd say above seventy or eighty
thousand feet.  We still get pretty distinct booms from the Shuttle
when it comes in, even at fifty thousand.  And on ascent, it's even
worse, because you get a focusing of the boom on a small region as it
accelerates downrange.  I've never run a trajectory analysis, but I
suspect that staying subsonic (the speed of which *decreases* with
altitude) through the atmosphere would totally kill your performance,
except for a two-stage (wiith a first stage shock-free supersonic
airbreather) that staged subsonically very high.


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From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Wed, 05 Apr 2000 17:09:26 GMT

Rand Simberg <simberg.interglobal@trash.org> wrote in message
news:38ed42f3.137163011@nntp.ix.netcom.com...
> On Wed, 05 Apr 2000 09:33:52 GMT, in a place far, far away, Ian
> Stirling <Inquisitor@I.am> made the phosphor on my monitor glow in
> such a way as to indicate that:
>
> Pretty much out of the atmosphere (I'd say above seventy or eighty
> thousand feet.  We still get pretty distinct booms from the Shuttle
> when it comes in, even at fifty thousand.  And on ascent, it's even
> worse, because you get a focusing of the boom on a small region as it
> accelerates downrange.

This isn't quite right.  It's not the acceleration -- while that does tend
to "crowd" the shock waves a bit, it's not that severe.  It's the pitchover
turn that focuses the boom, as the boom from several points along the
trajectory intercepts the same area on the ground.

The good news is that with a lifting trajectory (which I was just
running yesterday), given proper vehicle parameters, you can be
pulling *up* while accelerating, which *defocuses* the boom on
the ground (it focuses it at a point above you in the atmosphere,
but so what?).

> I've never run a trajectory analysis, but I
> suspect that staying subsonic (the speed of which *decreases* with
> altitude) through the atmosphere would totally kill your performance,
> except for a two-stage (wiith a first stage shock-free supersonic
> airbreather) that staged subsonically very high.

I'm waaay to busy to run this now, but I've been thinking about
the same thing -- and I suspect the same answer for a pure rocket
powered vehicle. Adding some airbreathing thrust might make this
possible to do -- but difficult.  On the other hand, depending on your
application, a boom only in the launch area needn't be too great an
operational difficulty.

----------------------------------------------------------------
"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <www.xcor-aerospace.com>                <jgreason@hughes.net>

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: Wed, 05 Apr 2000 18:14:40 GMT

On 05 Apr 2000 13:54:52 -0400, in a place far, far away, Steinn
Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
glow in such a way as to indicate that:

>> We submitted an unsolicited proposal to NASA (handed it directly to
>> Dan Goldin and Bob Whitehead) even before Congress appropriate the
>> money.  They circular filed it.  Later, after the funds were
>
>Yeah, I probably would have too if I'd been them.
>Bad schmooze tactic.

It's a bad schmooze tactic to submit an unsolicited proposal?

>> As I said, NASA looked at it, and rejected it, with no substantive
>> critique or description of why it would not work, except that we got
>> the impression that they considered shock waves to be some sort of law
>> of nature.
>
>Well, they are...

And what law of nature would that be?  Feinman disagreed with you.

>Well, I'm used to a different way of looking at shocks, but
>I think I get it, and I think I see why large sections of NASA
>tossed it without giving it a serious look.
>
>From my perspective, shock waves are intrinsic to supersonic
>motion, because there is no causal way for the fluid upstream
>to elastically respond to the displacement, and hence a pressure
>and density discontinuity develops which is intrinsic to the
>process. ie there must be a shock.

No, there must be a compression.  Shock is not intrinsically required.


>Now, as I read it, you are not actually stopping the shock,
>rather you are using the fact that you have privileged information
>(you can anticipate where the object is going and how fast and you
>can introduce additional flow inside the separatrix of the shock fronts)
>to reduce dissipation in part of the shock (potentially by a
>large factor). Normally as I look at it, the problem is that
>there is no communication in the fluid after it separates, hence
>the messy flow over the wing - but your technique optimises to
>some extent the recombination of the separated flows by injecting
>fluid on one side of the shock, anticipating the natural response
>of the fluid and pre-empting the flow patterns.

No, we are eliminating the shock, just as in an isentropic
diverging-converging nozzle--it's just that we've figured out a way to
do it and still get lift, which is the *real* trick.

>This seems permitted, and should work in principle, but
>in my language you have not got shock-free flight and you
>haven't abolished the presence of shocks at M > 1,
>rather you "just" have a method that might possibly drastically
>reduce the dissipation in the shock and make the rejoining
>of the two fluid streams down-shock be much nicer.
>
>Did you put it that way to the NASA folks, or the way
>you put it here just earlier?

The former, because that is what we believe we are doing.

>Cause my reaction to "no shock" or "shock free" would
>be "no way, crackpot" - but my reaction to "major reduction
>in dissipation in weak shocks" would be "hmm, could be
>interesting if made practical"...

Well, perhaps it would be easier to sell that way, but it wouldn't be
accurate.

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From: Steinn Sigurdsson <steinn@muon.astro.psu.edu>
Newsgroups: sci.space.policy
Subject: Re: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: 05 Apr 2000 14:33:41 -0400

simberg.interglobal@trash.org (Rand Simberg) writes:

> On 05 Apr 2000 13:54:52 -0400, in a place far, far away, Steinn
> Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
> glow in such a way as to indicate that:

> >> We submitted an unsolicited proposal to NASA (handed it directly to
> >> Dan Goldin and Bob Whitehead) even before Congress appropriate the
> >> money.  They circular filed it.  Later, after the funds were

> >Yeah, I probably would have too if I'd been them.
> >Bad schmooze tactic.

> It's a bad schmooze tactic to submit an unsolicited proposal?

No, it is a bad tactic to thrust an unsolicited proposal
directly at Dan Goldin.

Sometimes bypassing the normal channels backfires badly.
Anyway, odds on unsolicited proposals suck, why not
respond to a code R RFP? They must have some which could
be stretched to be considered relevant.

If you act as if you want to play outside the normal rules
it makes people suspicious that it is because you would lose
playing by the rules.
It is not necessarily fair or reasonable, just institutional
self-defence mechanisms.
Imagine if Goldin had to look over proposals from our
friendly "fractal-robot" nut - he has too much to do and
too little time as is.

> >> As I said, NASA looked at it, and rejected it, with no substantive
> >> critique or description of why it would not work, except that we got
> >> the impression that they considered shock waves to be some sort of law
> >> of nature.

> >Well, they are...

> And what law of nature would that be?  Feinman disagreed with you.

Well, Feynman forgot to mention this to me when
I took a class from him then. Or I forgot, which
is possible but unlikely. Or most likely, it never
came up - too many other things to say and too little time.

What are you calling a shock?
What I call a shock is a discontinuity in the
pressure and density of a fluid (averaged over
a suitable length scale) which occurs when
something moves through the fluid at a speed larger
than the local speed of sound.
The presence of a shock follows directly from the
pde's describing the response of a fluid.

> >Well, I'm used to a different way of looking at shocks, but
> >I think I get it, and I think I see why large sections of NASA
> >tossed it without giving it a serious look.

> >From my perspective, shock waves are intrinsic to supersonic
> >motion, because there is no causal way for the fluid upstream
> >to elastically respond to the displacement, and hence a pressure
> >and density discontinuity develops which is intrinsic to the
> >process. ie there must be a shock.

> No, there must be a compression.  Shock is not intrinsically required.

From your description I did not see that you eliminated
the discontinuity in the fluid - rather you damped out
some of the structure that develops in the fluid in response
to the discontinuity.
Not quite the same in my language.

> >Now, as I read it, you are not actually stopping the shock,
> >rather you are using the fact that you have privileged information
> >(you can anticipate where the object is going and how fast and you
> >can introduce additional flow inside the separatrix of the shock fronts)
> >to reduce dissipation in part of the shock (potentially by a
> >large factor). Normally as I look at it, the problem is that
> >there is no communication in the fluid after it separates, hence
> >the messy flow over the wing - but your technique optimises to
> >some extent the recombination of the separated flows by injecting
> >fluid on one side of the shock, anticipating the natural response
> >of the fluid and pre-empting the flow patterns.

> No, we are eliminating the shock, just as in an isentropic
> diverging-converging nozzle--it's just that we've figured out a way to
> do it and still get lift, which is the *real* trick.

Well, I think I understand what you say you are doing,
and in my language this would not be eliminating the shock
but eliminating the some of the effects of the shock.
Or I could be badly misunderstanding what you are saying.
Or what you call shock could be what I call an effect of the shock.

> >This seems permitted, and should work in principle, but
> >in my language you have not got shock-free flight and you
> >haven't abolished the presence of shocks at M > 1,
> >rather you "just" have a method that might possibly drastically
> >reduce the dissipation in the shock and make the rejoining
> >of the two fluid streams down-shock be much nicer.

> >Did you put it that way to the NASA folks, or the way
> >you put it here just earlier?

> The former, because that is what we believe we are doing.

So are you eliminating, globally, singularities in the
gradients of fluid variables?

> >Cause my reaction to "no shock" or "shock free" would
> >be "no way, crackpot" - but my reaction to "major reduction
> >in dissipation in weak shocks" would be "hmm, could be
> >interesting if made practical"...

> Well, perhaps it would be easier to sell that way, but it wouldn't be
> accurate.

If you want to sell things, you have to learn the language of
the customer...

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Shock-Free Supersonics (Was Breaking the ice)
Date: Wed, 05 Apr 2000 18:38:54 GMT

On Wed, 05 Apr 2000 18:17:43 GMT, in a place far, far away, Len
(Cormier) for MMI <len@tour2space.com> made the phosphor on my monitor
glow in such a way as to indicate that:


>Congratulations, Rand. Sounds like it might work.
>Have you been able to get any test data yet?

There was some wind tunnel work done at Ohio State, and LockMart
simulted it with CFD a few years ago.

>How
>about NASA?  This is a case where they should
>really support you.  It will be interesting whether
>or not NASA will favor the big aerospace companies
>with respect to support of futher investigations.

See my discussion with Steinn in the original thread.  NASA's
response, when Congress told them they had to look at it, was to throw
us a bone by trying to give a contract to LockMart to look at it and
having them get a small subcontract, even though we're the ones who
developed the technology...  Congress shut that down.

>Should they choose to do so, there are really no
>redeeming factors for the continuation of NASA.

You said it, not me...   :-)

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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: Wed, 05 Apr 2000 18:48:02 GMT

On 05 Apr 2000 14:33:41 -0400, in a place far, far away, Steinn
Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
glow in such a way as to indicate that:

>No, it is a bad tactic to thrust an unsolicited proposal
>directly at Dan Goldin.

Well, perhaps--I wasn't involved.

>Sometimes bypassing the normal channels backfires badly.
>Anyway, odds on unsolicited proposals suck, why not
>respond to a code R RFP? They must have some which could
>be stretched to be considered relevant.

>If you act as if you want to play outside the normal rules
>it makes people suspicious that it is because you would lose
>playing by the rules.
>It is not necessarily fair or reasonable, just institutional
>self-defence mechanisms.
>Imagine if Goldin had to look over proposals from our
>friendly "fractal-robot" nut - he has too much to do and
>too little time as is.

Yes.  Well, at any rate, we aren't looking to NASA for funding at this
point--we're seeking private investment.

>Well, Feynman forgot to mention this to me when
>I took a class from him then. Or I forgot, which
>is possible but unlikely. Or most likely, it never
>came up - too many other things to say and too little time.

Most likely the latter.

>What are you calling a shock?
>What I call a shock is a discontinuity in the
>pressure and density of a fluid (averaged over
>a suitable length scale) which occurs when
>something moves through the fluid at a speed larger
>than the local speed of sound.
>The presence of a shock follows directly from the
>pde's describing the response of a fluid.

We agree on what a shock is, but there are theoretical ways of
avoiding it, (though it will always be there, in the same sense that
there are no frictionless pulleys, etc.)  Our argument is with those
who say that it is theoretically required.

>> No, there must be a compression.  Shock is not intrinsically required.
>
>From your description I did not see that you eliminated
>the discontinuity in the fluid - rather you damped out
>some of the structure that develops in the fluid in response
>to the discontinuity.

No, in theory we can eliminate the discontinuities--Crocco tells us
so.  In practice, we can only minimize them to insignificant levels.

>> No, we are eliminating the shock, just as in an isentropic
>> diverging-converging nozzle--it's just that we've figured out a way to
>> do it and still get lift, which is the *real* trick.
>
>Well, I think I understand what you say you are doing,
>and in my language this would not be eliminating the shock
>but eliminating the some of the effects of the shock.
>Or I could be badly misunderstanding what you are saying.
>Or what you call shock could be what I call an effect of the shock.

No, I think that we're talking about shock.

>> >This seems permitted, and should work in principle, but
>> >in my language you have not got shock-free flight and you
>> >haven't abolished the presence of shocks at M > 1,
>> >rather you "just" have a method that might possibly drastically
>> >reduce the dissipation in the shock and make the rejoining
>> >of the two fluid streams down-shock be much nicer.
>
>> >Did you put it that way to the NASA folks, or the way
>> >you put it here just earlier?
>
>> The former, because that is what we believe we are doing.
>
>So are you eliminating, globally, singularities in the
>gradients of fluid variables?

On paper (and perhaps even in CFD), yes.  In a real-world airplane,
no, but we can have practical cars even with some friction in the
drive train.  Current supersonic design doesn't even really attempt to
minimize it.  We are attempting to eliminate it, which will result in
a dramatic minimization.

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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Shock-Free Supersonics (Was Breaking the ice)
Date: Wed, 05 Apr 2000 18:49:16 GMT

On Wed, 05 Apr 2000 18:38:54 GMT, in a place far, far away,
simberg.interglobal@trash.org (Rand Simberg) made the phosphor on my
monitor glow in such a way as to indicate that:

>See my discussion with Steinn in the original thread.  NASA's
>response, when Congress told them they had to look at it, was to throw
>us a bone by trying to give a contract to LockMart to look at it and
>having them get a small subcontract, even though we're the ones who

Whoops!  That should read "having them give us a small subcontract.."

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From: Steinn Sigurdsson <steinn@muon.astro.psu.edu>
Newsgroups: sci.space.policy
Subject: Re: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: 05 Apr 2000 15:03:17 -0400

simberg.interglobal@trash.org (Rand Simberg) writes:

> On 05 Apr 2000 14:33:41 -0400, in a place far, far away, Steinn
> Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
> glow in such a way as to indicate that:

> >From your description I did not see that you eliminated
> >the discontinuity in the fluid - rather you damped out
> >some of the structure that develops in the fluid in response
> >to the discontinuity.

> No, in theory we can eliminate the discontinuities--Crocco tells us
> so.  In practice, we can only minimize them to insignificant levels.

Ok, I don't see how the process you outlined can eliminate
the shock globally - it seems to explicitly only deal with
a local portion of the shock and from the description
it seemed to me you'd still have a true shock in front
of and above the aircraft, but that gets into details
that aren't communicable in ASCII on usenet.
I'm obviously missing something about the process.

I can't see how the procedure you describe can eliminate
the global shock - the causal problem remains - but I can
see how the process _could_ minimize shocks.

The open question would then be whether it is practical,
and whether there is some other penalty that makes the
technology not worth while - which begs for research
and flight tests - and a formal code R proposal should either
have been accepted or rejected with an explanation
which would then be open to rebuttal.

On the whole NASA issue there are three possibilities:

1) NASA looked at this and knows why it is wrong

2) NASA isn't interested because they are bad

3) NASA would be interested but the right people
haven't got the point because of poor communication

My money is on 3, with 1 a runner-up (but they should
then tell you) and I tire of 2 as an argument.
Seems to me the obligation is on you to communicate
the issue to NASA, while NASA has some obligation in
turn to actually listen.

Newsgroups: sci.space.policy
From: henry@spsystems.net (Henry Spencer)
Subject: shockless flight (was Re: Loan Guarantees for Launch Vehicles)
Date: Thu, 6 Apr 2000 04:27:24 GMT

In article <rx7ya6sph5f.fsf@muon.astro.psu.edu>,
Steinn Sigurdsson  <steinn@muon.astro.psu.edu> wrote:
>From my perspective, shock waves are intrinsic to supersonic
>motion, because there is no causal way for the fluid upstream
>to elastically respond to the displacement, and hence a pressure
>and density discontinuity develops which is intrinsic to the
>process. ie there must be a shock.

Nope.  As I understand it, shockless supersonic shapes were demonstrated
long ago.  (I'd heard about this, in obscure places, well before I ran
into the concept Rand's talking about.)  They have been a minor textbook
curiosity, rather than a practical design approach, because there seemed
to be no way to get *lift* out of them.

The classic trick is to put a ring around the main body at just the right
place, reflecting the nose shock back to the main body.  There, it tries
to reflect off the main body again... and if you arrange the shapes just
right, it's superimposed on an expansion-wave fan coming off the main body
just there, canceling it out.  You get a local shock, but no radiated one.
(There's no shock outward off the ring because its outer edge is parallel
to the surrounding airflow and hence does not disturb it, in principle.)
The details have to be just so, and non-ideal behavior will produce some
slight radiated shock in practice, but it can be quite small.

In Shapiro ("The dynamics and thermodynamics of compressible fluid flow",
2 vols, 1954), see pages 451-2 for theory of such cancellation and
wind-tunnel photos of it (in a simpler system), and pages 688-690 for
theory of a centerbody-plus-ring shape which could fly -- at zero angle of
attack -- without a radiated shock and with quite low wave drag.

The trick is applying this to a *wing*.  Shapiro discusses the "Busemann
biplane" shape which is a (theoretically) shock-free wing, but only at
zero angle of attack, where it generates no lift because it uses two
identical wing surfaces facing each other.  The air jet Rand describes is
more or less a way of substituting smoke and mirrors :-) for one surface
of the Busemann biplane.  Sounds plausible to me, but as noted before, an
aerodynamicist I'm not...
--
"Be careful not to step                 |  Henry Spencer   henry@spsystems.net
in the Microsoft."  -- John Denker      |      (aka henry@zoo.toronto.edu)

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Loan Guarantees for Launch Vehicles
Date: Thu, 06 Apr 2000 06:10:08 GMT

On Wed, 05 Apr 2000 21:30:44 -0500, in a place far, far away, James A
Davis <jimdavis2@primary.net> made the phosphor on my monitor glow in
such a way as to indicate that:

>Glad to see you're finally allowed to speak of this. Is there or will
>there soon be a published or conference paper describing the technique
>in greater detail than is possible here? I would like to take a closer
>look.

Possibly, but nothing definite yet.

>> OK, here's a brief summary.  Shock waves are nature's way of providing
>> a reaction to the wing circulation in supersonic flight.  In subsonic
>> flight (as Prandtl discovered) there is a bound vortex around the
>> wing, and an uplift of the air upstream to allow the downturn behind
>> to provide lift.  This can't happen in supersonic flight, because the
>> air up ahead doesn't know the airplane is coming.  So instead, shock
>> waves form off the leading edge, which interact with the expansion
>> fans to form vortex sheets.  The net sum of these sheets and the wing
>> circulation add up to zero to conserve angular momentum, but it's very
>> inefficient, because the vortex sheets are of both signs, and generate
>> a lot more momentum (absolute magnitude) than is required to simply
>> balance the circulation.  They result in a lot of heating of the air
>> in the wake (where most of the energy goes--the sonic boom is a tiny
>> percentage of it), which of course contributes not at all to moving
>> the airplane, hence the high fuel costs for supersonic flight.
>
>The paragraph above appears to imply that shock waves are only produced
>by lifting surfaces which is, of course, not the case.

Didn't mean to imply that.  This discussion only pertained to lifting
surfaces.

>Does your method
>work for non lifting surfaces?

The method described above does not, but there are other techniques
for non-lifting surfaces, such as designing them like a low-entropy
nozzle (i.e. put a cowl around them to capture the shock energy on the
inner surface.  See Ferri's work on a shockless fuselage of a few
decades ago.  The inlet to the SR-71 engine also operates on this
principal.

>If not, is the general effect of your
>technique to reduce the wave drag of a lifting surface at an angle of
>attack at which it produces lift to the wave drag of the same surface at
>the angle of attack at which no lift is produced?

Ummmm, if I understand the question, I don't think so.  In fact, it is
essential that the angle of attack be zero--any other angle will
induce a shock.

>> We've solved the problem by creating an artificial reaction to the
>	^^^^^^
>Surely this is somewhat premature? If you're this confident of your
>solution why bother going to NASA for testing?

Solved the problem in a theoretical feasibility sense.  There are
still many questions about geometries, mixing velocities, etc., to
optimize it to full effect.  This can only be determined by extensive
CFD research.  There are also many practical issues (obviously).

>If I understand your explanation correctly you are attempting to add
>energy to the flow by means of mass transport. The Crocco relation
>applies to a fluid element of constant mass and has no terms for mass
>transport (mass diffusivity) and momentum transport (viscosity) across
>the element boundary. It seems to me you need more to add more terms
>than the total specific enthalpy gradient to Crocco's relation for a
>meaningful analysis. But perhaps you've done so...
>
>My experience has been (with supersonic combustors) that injecting
>fluids into a supersonic flow produces more shocks, not less so I remain
>skeptical. I would like to take a closer look, though.

It is certainly possible to add flow and produce more shocks, if you
don't do it right <g>.  The question is whether it is possible to do
it to eliminate shock.  The math, the preliminary wind tunnel tests,
and the CFD indicate that it is.

>The details could stand to be fleshed out a little!

They have been, much more so that I can produce on Usenet right now.
I hope that we will be able to publish soon.  I'd like to put stuff on
the web myself, but there's still some concern about showing too much
too soon.

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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: Thu, 06 Apr 2000 06:42:15 GMT

On 05 Apr 2000 15:03:17 -0400, in a place far, far away, Steinn
Sigurdsson <steinn@muon.astro.psu.edu> made the phosphor on my monitor
glow in such a way as to indicate that:

>> No, in theory we can eliminate the discontinuities--Crocco tells us
>> so.  In practice, we can only minimize them to insignificant levels.
>
>Ok, I don't see how the process you outlined can eliminate
>the shock globally - it seems to explicitly only deal with
>a local portion of the shock and from the description
>it seemed to me you'd still have a true shock in front
>of and above the aircraft, but that gets into details
>that aren't communicable in ASCII on usenet.

Well, yes, I didn't describe how we get rid of shock on the fuselage,
which is a separate subject (that I describe briefly in the post to
Jim Davis).

>I'm obviously missing something about the process.

Understandably, since I've been describing it in a very abbreviated
manner.

>I can't see how the procedure you describe can eliminate
>the global shock - the causal problem remains - but I can
>see how the process _could_ minimize shocks.

Well, that's enough for now.  I'm sure you'd agree that even that is a
big breakthrough.

>The open question would then be whether it is practical,
>and whether there is some other penalty that makes the
>technology not worth while - which begs for research
>and flight tests - and a formal code R proposal should either
>have been accepted or rejected with an explanation
>which would then be open to rebuttal.
>
>On the whole NASA issue there are three possibilities:
>
>1) NASA looked at this and knows why it is wrong
>
>2) NASA isn't interested because they are bad
>
>3) NASA would be interested but the right people
>haven't got the point because of poor communication
>
>My money is on 3, with 1 a runner-up (but they should
>then tell you) and I tire of 2 as an argument.
>Seems to me the obligation is on you to communicate
>the issue to NASA, while NASA has some obligation in
>turn to actually listen.

Well, I think that it's a combination of a modified 2 and 3.  It's
certainly not 1, or if it is, they could never articulate either to us
or to Congress why it was wrong.   (Modified 2 in that it's not that
NASA is "bad" but rather that some parts of NASA are obtuse, and some
parts of NASA get emotionally attached to major programs that might be
put at risk by new ideas, and much of NASA is majorly disfunctional.)
There is a great deal of 3, in that the people that we were trying to
persuade (because they were the ones that HQ gave the money to for the
program) were the HSCT designers at Langley, who seemed to be, to a
man (and woman), aircraft designers rather than theoretical
aerodynamicists.  We did communicate to the aero guys at Ames, and
they were very interested in pursuing the technology, but had to back
off after Langley threatened to cut off their CFD funding for the HSR
program...

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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: shockless flight (was Re: Loan Guarantees for Launch Vehicles)
Date: Thu, 06 Apr 2000 07:04:23 GMT

On Thu, 6 Apr 2000 04:27:24 GMT, in a place far, far away,
henry@spsystems.net (Henry Spencer) made the phosphor on my monitor
glow in such a way as to indicate that:

>In article <rx7ya6sph5f.fsf@muon.astro.psu.edu>,
>Steinn Sigurdsson  <steinn@muon.astro.psu.edu> wrote:
>>From my perspective, shock waves are intrinsic to supersonic
>>motion, because there is no causal way for the fluid upstream
>>to elastically respond to the displacement, and hence a pressure
>>and density discontinuity develops which is intrinsic to the
>>process. ie there must be a shock.
>
>Nope.  As I understand it, shockless supersonic shapes were demonstrated
>long ago.  (I'd heard about this, in obscure places, well before I ran
>into the concept Rand's talking about.)  They have been a minor textbook
>curiosity, rather than a practical design approach, because there seemed
>to be no way to get *lift* out of them.

Yes, and in fact, the same company that came up with this concept also
developed a shock-free bullet for the army two or three decades ago.
Handy for snipers, who don't want their targets to know that they're
being shot at if they miss.

It was basically a converging/diverging nozzle, rifled for spin
stability.  The trick was to get the proper contour and throat sizing
so that it didn't choke.

>The classic trick is to put a ring around the main body at just the right
>place, reflecting the nose shock back to the main body.  There, it tries
>to reflect off the main body again... and if you arrange the shapes just
>right, it's superimposed on an expansion-wave fan coming off the main body
>just there, canceling it out.  You get a local shock, but no radiated one.
>(There's no shock outward off the ring because its outer edge is parallel
>to the surrounding airflow and hence does not disturb it, in principle.)
>The details have to be just so, and non-ideal behavior will produce some
>slight radiated shock in practice, but it can be quite small.

Well, it may be a terminology problem again, but we would say that you
don't even get a local shock--just compression waves that are never
permitted to coalesce into shock waves.

>The trick is applying this to a *wing*.  Shapiro discusses the "Busemann
>biplane" shape which is a (theoretically) shock-free wing, but only at
>zero angle of attack, where it generates no lift because it uses two
>identical wing surfaces facing each other.  The air jet Rand describes is
>more or less a way of substituting smoke and mirrors :-) for one surface
>of the Busemann biplane.  Sounds plausible to me, but as noted before, an
>aerodynamicist I'm not...

Yes, and the key is that it is an active, dynamic lower surface, that
can generate a circulation to provide lift, rather than a static one,
as in Busemann's concept.  The trick is to figure out how to optimize
it to reflect all of the wave energy back onto the upper wing.  The
degree to which you fail to do this (and the degree to which the
leading edge is less than razor sharp and the upper surface of the
upper wing less than perfectly flat) will generate some shock entropy.


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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Thu, 06 Apr 2000 18:19:29 GMT

On Wed, 05 Apr 2000 21:30:44 -0500, in a place far, far away, James A
Davis <jimdavis2@primary.net> made the phosphor on my monitor glow in
such a way as to indicate that:

One more follow-up, and hopefully another diversion to a more
appropriately-titled thread.

>If I understand your explanation correctly you are attempting to add
>energy to the flow by means of mass transport. The Crocco relation
>applies to a fluid element of constant mass and has no terms for mass
>transport (mass diffusivity) and momentum transport (viscosity) across
>the element boundary. It seems to me you need more to add more terms
>than the total specific enthalpy gradient to Crocco's relation for a
>meaningful analysis. But perhaps you've done so...

I'm not sure what you mean by the "Crocco relation."  The equation to
which I'm referring describes a vector flow field and is:

	T*grad(s) + q x curl(q) = grad(h + (q dot q)/2)

where T is temperature, s is entropy, q is a velocity vector and h is
the stagnation enthalpy.  In terms of this discussion, the first term
could be considered the shock term, the second one the wing
circulation (corresponding to lift) and the one on the right-hand side
the energy gradient.  Historically (for a good treatment see the
General Theory of High-Speed Aerodynamics Vol VI Section D, Princeton
University Press, 1954,  pp.328-329 by Heaslet and Lomax at Ames), we
get the form that most are familiar with by arguing that at cruise,
the enthalpy and velocity of the flow are constant, so we can say that
the gradient of the constant goes to zero, and we throw the term away,
ending up with an equivalence between the circulation and the shock
term.  If we try to zero the shock term, as in Busemann's concept, we
can do so, but we also lose the circulation (with its corresponding
lift), and the airplane falls out of the sky...

IOW, if one wants to get aerodynamic lift without adding energy to the
flow, shock is indeed a law of nature, and every supersonic airplane
we've ever built, from X-1 through Concorde, demonstrates this.

OTOH, the math indicates that if we choose to introduce an energy
change, we can in theory zero out the entropy term instead while
retaining the wing circulation.  So, since we have engines on our
airplane, we use some of their energy to improve wing efficiency.  But
the equation in itself says nothing about how to change the energy to
zero out the shock, and that's what we have to investigate to get a
practical aircraft design.

Now, this was just preparatory to addressing what I think is your
question.  You say that the equation is based on a mass element, and
that we aren't adding energy to that mass element by introducing an
air jet.  I guess my argument is that we are, because that jet will
interact with the element to change its (and all of its neighbors')
velocity.  It will likely also affect its enthalpy, but that's not
necessary to make the point.

Does that make sense?

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From: James A Davis <jimdavis2@primary.net>
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: 2000/04/06
Message-ID: <38ED2EAC.5CF2B1A@primary.net>
Newsgroups: sci.space.policy

Rand Simberg wrote:

> I'm not sure what you mean by the "Crocco relation."

The same equation you reproduce below. Also known as Crocco's theorem.
I'll use your term.

> The equation to
> which I'm referring describes a vector flow field and is:
>
>         T*grad(s) + q x curl(q) = grad(h + (q dot q)/2)
>
> where T is temperature, s is entropy, q is a velocity vector and h is
> the stagnation enthalpy.  In terms of this discussion, the first term
> could be considered the shock term, the second one the wing
> circulation (corresponding to lift)

It's important to note that the second term involves the fluid vorticity
[curl(q)] which is related to but not identical to wing circulation. The
wing circulation is the surface integral of the fluid vorticity. The
flow can be highly rotational and the circulation (and hence lift) can
still be zero but the flow cannot be irrotational without the
circulation being zero.

> and the one on the right-hand side
> the energy gradient.  Historically (for a good treatment see the
> General Theory of High-Speed Aerodynamics Vol VI Section D, Princeton
> University Press, 1954,  pp.328-329 by Heaslet and Lomax at Ames), we
> get the form that most are familiar with by arguing that at cruise,
> the enthalpy and velocity of the flow are constant, so we can say that
> the gradient of the constant goes to zero, and we throw the term away,
> ending up with an equivalence between the circulation and the shock
> term.  If we try to zero the shock term, as in Busemann's concept, we
> can do so, but we also lose the circulation (with its corresponding
> lift), and the airplane falls out of the sky...

Again (and I appreciate that you are simplifying) it's worth pointing
out that it's quite possible to have very strong shocks with no
circulation (and hence lift). A sphere (Vostok) in a supersonic flow,
for example.

> IOW, if one wants to get aerodynamic lift without adding energy to the
> flow, shock is indeed a law of nature, and every supersonic airplane
> we've ever built, from X-1 through Concorde, demonstrates this.

> OTOH, the math indicates that if we choose to introduce an energy
> change, we can in theory zero out the entropy term instead while
> retaining the wing circulation.  So, since we have engines on our
> airplane, we use some of their energy to improve wing efficiency.  But
> the equation in itself says nothing about how to change the energy to
> zero out the shock, and that's what we have to investigate to get a
> practical aircraft design.
>
> Now, this was just preparatory to addressing what I think is your
> question.  You say that the equation is based on a mass element, and
> that we aren't adding energy to that mass element by introducing an
> air jet.  I guess my argument is that we are, because that jet will
> interact with the element to change its (and all of its neighbors')
> velocity.  It will likely also affect its enthalpy, but that's not
> necessary to make the point.
>
> Does that make sense?

Of course. My concern though is this:

The Crocco equation applies only to an inviscid flow (its derivation
uses the Euler equation

	rho [partial q / partial t + ( q dot grad)q] = - grad p

which has no viscosity terms in it). The only way your jet can transfer
energy to the fluid elements in the freestream is by a.) radiation
(negligible), b.) conduction (minor at these speeds), and c.) by doing
work on the fluid elements by pressure and shear forces. Clearly,
viscosity is going to be a major means of transferring energy to the
freestream fluid elements but viscosity terms are not present in the
Crocco equation.

Jim Davis

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Fri, 07 Apr 2000 02:19:54 GMT

On Thu, 06 Apr 2000 19:41:16 -0500, in a place far, far away, James A
Davis <jimdavis2@primary.net> made the phosphor on my monitor glow in
such a way as to indicate that:

>It's important to note that the second term involves the fluid vorticity
>[curl(q)] which is related to but not identical to wing circulation. The
>wing circulation is the surface integral of the fluid vorticity. The
>flow can be highly rotational and the circulation (and hence lift) can
>still be zero but the flow cannot be irrotational without the
>circulation being zero.

Yes, though I'm not sure that this changes the basic point.

>Again (and I appreciate that you are simplifying) it's worth pointing
>out that it's quite possible to have very strong shocks with no
>circulation (and hence lift). A sphere (Vostok) in a supersonic flow,
>for example.

Sure.  We can zero the lift term if we want, though this would be poor
aircraft design <g>.

>My concern though is this:
>
>The Crocco equation applies only to an inviscid flow (its derivation
>uses the Euler equation
>
>	rho [partial q / partial t + ( q dot grad)q] = - grad p
>
>which has no viscosity terms in it). The only way your jet can transfer
>energy to the fluid elements in the freestream is by a.) radiation
>(negligible), b.) conduction (minor at these speeds), and c.) by doing
>work on the fluid elements by pressure and shear forces. Clearly,
>viscosity is going to be a major means of transferring energy to the
>freestream fluid elements but viscosity terms are not present in the
>Crocco equation.

First of all, congratulations.  This is the first substantive
technical objection that I've gotten from *anyone* after four years of
interaction with Steinn's beloved air and space agency (not to imply
that you work for them).

I guess I'm a little confused by your objection. Of course viscosity
is a major contributor to transferring the energy.  But Crocco's
Theorem (to use your, possible more correct, terminology) is directly
derived (though I won't bore with the derivation) from the basic laws
of thermodynamics and conservation of energy and angular momentum.  To
say that Crocco won't apply because I'm not including viscosity is (at
least to me) like saying that F = dp/dt doesn't apply because I'm not
explicitly including friction.

Am I missing something?  Are you saying that this is a fundamental
flaw and that this therefore won't work, or are you saying that you
are concerned that it may not work due to this issue?  If the former,
you'll need to provide a more rigorous proof.

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From: James A Davis <jimdavis2@primary.net>
Newsgroups: sci.space.policy
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Thu, 06 Apr 2000 22:38:02 -0500

Rand Simberg wrote:

> First of all, congratulations.  This is the first substantive
> technical objection that I've gotten from *anyone* after four years of
> interaction with Steinn's beloved air and space agency (not to imply
> that you work for them).

Thanks...I think. By the way, precisely what is your relation to this
concept anyway? Originator, co-originator, promoter, agent or something
else?

> I guess I'm a little confused by your objection. Of course viscosity
> is a major contributor to transferring the energy.  But Crocco's
> Theorem (to use your, possible more correct, terminology) is directly
> derived (though I won't bore with the derivation) from the basic laws
> of thermodynamics and conservation of energy and angular momentum.  To
> say that Crocco won't apply because I'm not including viscosity is (at
> least to me) like saying that F = dp/dt doesn't apply because I'm not
> explicitly including friction.

Crocco's Theorem was derived by making certain assumptions about the
flowfield to which it would be applied. One of the assumptions was that
the flowfield was inviscid. As long as this is approximately the case
Crocco's Theorem applies. If not, then it has to be modified
accordingly.

Describing a couple of similar cases might be in order. The rocket
equation [v = ve ln(M)] is derived from the basic law of conservation of
momentum. But this equation is derived assuming that drag and gravity
loss terms can be neglected. True under many important situations but
not under others. In these cases more terms must be added.

Similarly, Bernoulli's equation [p + rho v^2 /2 = C] is also derived
from the basic laws of momentum and mass conservation. But its
derivation assumes that the flow is incompressible, i.e. rho is a
constant. Again, a reasonable assumption for some conditions, not for
others.

> Am I missing something?  Are you saying that this is a fundamental
> flaw and that this therefore won't work, or are you saying that you
> are concerned that it may not work due to this issue?  If the former,
> you'll need to provide a more rigorous proof.

I'm saying the latter. It seems to me that you're applying Crocco's
Theorem in a situation (large velocity gradients where viscosity can't
be neglected) where that might not be appropriate. Sort of like using
Bernoulli's equation in the same situation.

Whether this is a fatal flaw or not, I can't say.

Jim Davis

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Fri, 07 Apr 2000 04:04:46 GMT

On Thu, 06 Apr 2000 22:38:02 -0500, in a place far, far away, James A
Davis <jimdavis2@primary.net> made the phosphor on my monitor glow in
such a way as to indicate that:

>> First of all, congratulations.  This is the first substantive
>> technical objection that I've gotten from *anyone* after four years of
>> interaction with Steinn's beloved air and space agency (not to imply
>> that you work for them).
>
>Thanks...I think. By the way, precisely what is your relation to this
>concept anyway? Originator, co-originator, promoter, agent or something
>else?

Promoter, agent, someone very interested in seeing it happen and
incidentally getting sick rich as a result, possibly officer upon
significant funding...

Interested in getting involved?

>> I guess I'm a little confused by your objection. Of course viscosity
>> is a major contributor to transferring the energy.  But Crocco's
>> Theorem (to use your, possible more correct, terminology) is directly
>> derived (though I won't bore with the derivation) from the basic laws
>> of thermodynamics and conservation of energy and angular momentum.  To
>> say that Crocco won't apply because I'm not including viscosity is (at
>> least to me) like saying that F = dp/dt doesn't apply because I'm not
>> explicitly including friction.
>
>Crocco's Theorem was derived by making certain assumptions about the
>flowfield to which it would be applied. One of the assumptions was that
>the flowfield was inviscid. As long as this is approximately the case
>Crocco's Theorem applies. If not, then it has to be modified
>accordingly.

Do you have the modifications?  We might be able to resolve the issue
by simply inspecting the more complete form of the equation.

>> Am I missing something?  Are you saying that this is a fundamental
>> flaw and that this therefore won't work, or are you saying that you
>> are concerned that it may not work due to this issue?  If the former,
>> you'll need to provide a more rigorous proof.
>
>I'm saying the latter. It seems to me that you're applying Crocco's
>Theorem in a situation (large velocity gradients where viscosity can't
>be neglected) where that might not be appropriate. Sort of like using
>Bernoulli's equation in the same situation.
>
>Whether this is a fatal flaw or not, I can't say.

OK.  That's reasonable.  I guess that where we're at is that we've got
some fundamental derivations, some solid basic theory, and a lot more
than I've shown here, and we have some initial results from a wind
tunnel test (forty percent reduction in wave drag) and CFD (~80%
reduction) that are very encouraging.  So, as I said to Steinn, even
if we can't completely eliminate the drag, at least we're trying,
which is more than NASA has ever done or been willing to even attempt,
and we're bound to get a much more economically viable system as a
result.

I think that the real point is that in the 1920's, Prandtl and his
cohorts at Goettingen pretty much figured out subsonic aerodynamics,
and that provided the basis for much of the advance that we saw
through the thirties and forties, and got us through WWII and gave us
the modern air transport industry.  We (the aerodynamics community)
never established a similar scientific basis for supersonic flight.
We ploughed through the shock in 1947, characterized the hell out of
it, accepted it as inevitable, and that set the pace for the next
fifty years for the military, which could afford the fuel costs, and
didn't give a damn about booms, since their job in the first place was
to kill folks and break their stuff.

But it didn't make for viable supersonic commercial transportation.
We're trying to rectify that situation, and we could use some help...

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From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Continued Shock Discussion (was Re: Loan Guarantees for Launch 
	Vehicles)
Date: Fri, 07 Apr 2000 14:16:48 GMT

On Fri, 07 Apr 2000 21:08:56 +1200, in a place far, far away,
brucehoult@pobox.com (Bruce Hoult) made the phosphor on my monitor
glow in such a way as to indicate that:

>> No, we are eliminating the shock, just as in an isentropic
>> diverging-converging nozzle--it's just that we've figured out a way to
>> do it and still get lift, which is the *real* trick.
>
>What is the ratio of lift acheived to the static reaction force you'd get
>from the same air jet?

????

If I understand your question, you're asking how much lift we get out
of the wing at supersonic speeds compared to the thrust of the air jet
if it were directed downwards, instead of backwards?

Almost infinitesimal.  The total T/W of the engines on the plane, like
all tranports, would be less than one, and we're only drawing a small
percentage of the bleed air from the compressor first stage for the
jet.  Now since in fact, we direct it backward under the wing (same
direction as the thrust of the main propulsion), we aren't losing any
of the thrust, other than inefficiencies in transferring from the
engines into the jet manifold (low since it occurs at very high
pressure and very low velocity).

>I suspect that what you've got is not so much a wing with no shock at
>non-zero lift, as a way to shield a Harrier-style lifting jet so that it
>a) still works, abd b) doesn't produce a shock at supersonic speeds.

No, that's not it at all.

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From: James A Davis <jimdavis2@primary.net>
Newsgroups: sci.space.policy
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Fri, 07 Apr 2000 22:09:33 -0500

Rand Simberg wrote:

> >Thanks...I think. By the way, precisely what is your relation to this
> >concept anyway? Originator, co-originator, promoter, agent or something
> >else?
>
> Promoter, agent, someone very interested in seeing it happen and
> incidentally getting sick rich as a result, possibly officer upon
> significant funding...
>
> Interested in getting involved?

If that's an invitation, thanks, but no thanks, I'm overcommited as it
is. Besides, I don't want to do anything that might jeopardize my
amateur status.

> >Crocco's Theorem was derived by making certain assumptions about the
> >flowfield to which it would be applied. One of the assumptions was that
> >the flowfield was inviscid. As long as this is approximately the case
> >Crocco's Theorem applies. If not, then it has to be modified
> >accordingly.
>
> Do you have the modifications?  We might be able to resolve the issue
> by simply inspecting the more complete form of the equation.

Well, you asked for it.

T grad(s) = grad(ht) - v' x curl(v') + d'v'/d't + div(tau[ij])

where

tauij = d'/d'x[j] { mu (d'v[i]/d'x[j] + d'v[j]/d'x[i])
		+ del[ij] lambda div(v')}

and

Quantities

T - temperature
s - specific entropy
ht - specific stagnation enthalpy
v' - velocity vector
v - component of velocity vector
t - time
tau[ij] - shear stress tensor
mu - viscosity coefficient
lambda - bulk viscosity coefficient
del[ij] - delta function, del = 1, if i=j, otherwise del = 0

Operators

x - cross (vector) product
d' - partial derivative
grad - gradient operator
div - divergence operator
curl - curl operator

i,j - indices, repeated indices imply summation, one unrepeated index is
a vector quantity, two unrepeated indices is a tensor quantity

> OK.  That's reasonable.  I guess that where we're at is that we've got
> some fundamental derivations, some solid basic theory, and a lot more
> than I've shown here, and we have some initial results from a wind
> tunnel test (forty percent reduction in wave drag) and CFD (~80%
> reduction) that are very encouraging.  So, as I said to Steinn, even
> if we can't completely eliminate the drag, at least we're trying,
> which is more than NASA has ever done or been willing to even attempt,
> and we're bound to get a much more economically viable system as a
> result.

Well, to be fair, a lot of your problem has to do with your own
insistence on secrecy up until now. There are basically two ways to get
professional critiques of a new idea - 1.) pay for it (expensive) and
2.) publish papers and present at conferences so interest parties will
do it for free. The second option is incompatible with being "very
interested in getting sick rich" but there you have it.

> I think that the real point is that in the 1920's, Prandtl and his
> cohorts at Goettingen pretty much figured out subsonic aerodynamics,
> and that provided the basis for much of the advance that we saw
> through the thirties and forties, and got us through WWII and gave us
> the modern air transport industry.  We (the aerodynamics community)
> never established a similar scientific basis for supersonic flight.
> We ploughed through the shock in 1947, characterized the hell out of
> it, accepted it as inevitable, and that set the pace for the next
> fifty years for the military, which could afford the fuel costs, and
> didn't give a damn about booms, since their job in the first place was
> to kill folks and break their stuff.

Well, this is very unfair. It is no more accurate to say that supersonic
aerodynamics isn't on a firm scientific basis because shock waves can't
be eliminated than to say astronautics isn't on a firm scientific basis
because gravity can't be eliminated. Note that Prandtl and the Gottingen
crowd characterized the hell out of the boundary layer but didn't do a
lot about eliminating it...

> But it didn't make for viable supersonic commercial transportation.
> We're trying to rectify that situation, and we could use some help...

My advice, for what it might be worth, would be to pursue opportunities
to eliminate shock waves in *subsonic* applications, at least initially.
Commercial airliners whose wings don't have to be swept back, propellers
whose efficiency isn't limited by Mach effects at high tip speeds, etc.

Jim Davis

From: simberg.interglobal@trash.org (Rand Simberg)
Newsgroups: sci.space.policy
Subject: Re: Crocco's Equation (was Re: Loan Guarantees for Launch Vehicles)
Date: Sat, 08 Apr 2000 03:33:10 GMT

On Fri, 07 Apr 2000 22:09:33 -0500, in a place far, far away, James A
Davis <jimdavis2@primary.net> made the phosphor on my monitor glow in
such a way as to indicate that:

>> Interested in getting involved?
>
>If that's an invitation, thanks, but no thanks, I'm overcommited as it
>is. Besides, I don't want to do anything that might jeopardize my
>amateur status.

OK, that's cool.

>Well, you asked for it.

Indeed...

<expanded version of Crocco snipped>

Great!  Let me look it over (and possibly get some additional eyes on
it).


>Well, to be fair, a lot of your problem has to do with your own
>insistence on secrecy up until now. There are basically two ways to get
>professional critiques of a new idea - 1.) pay for it (expensive) and
>2.) publish papers and present at conferences so interest parties will
>do it for free. The second option is incompatible with being "very
>interested in getting sick rich" but there you have it.

Well, there's actually a third way, which is to get high-level profs
looking at it.  It's been vetted by several faculty members of the
Aero Department at Cal Tech, who will be involved with the development
if/when we get funding.  Of course, the fact that at least some of
them stand to benefit from funding it could create a conflict of
interest, so you'll have to decide if this will override their
academic integrity in the matter.

>> I think that the real point is that in the 1920's, Prandtl and his
>> cohorts at Goettingen pretty much figured out subsonic aerodynamics,
>> and that provided the basis for much of the advance that we saw
>> through the thirties and forties, and got us through WWII and gave us
>> the modern air transport industry.  We (the aerodynamics community)
>> never established a similar scientific basis for supersonic flight.
>> We ploughed through the shock in 1947, characterized the hell out of
>> it, accepted it as inevitable, and that set the pace for the next
>> fifty years for the military, which could afford the fuel costs, and
>> didn't give a damn about booms, since their job in the first place was
>> to kill folks and break their stuff.
>
>Well, this is very unfair. It is no more accurate to say that supersonic
>aerodynamics isn't on a firm scientific basis because shock waves can't
>be eliminated than to say astronautics isn't on a firm scientific basis
>because gravity can't be eliminated.

Now that's even more unfair.  Until you can point to the law of
physics that requires shock waves, that's not a valid comparison.

>Note that Prandtl and the Gottingen crowd characterized the hell out of
>the boundary layer but didn't do a lot about eliminating it...

Perhaps because that *would* violate some basic physics?  The point is
that they established a basis for practical subsonic flight.  No one
has done the same for supersonics.  Perhaps it's not possible, but at
least we, unlike NASA, are making the attempt.

>> But it didn't make for viable supersonic commercial transportation.
>> We're trying to rectify that situation, and we could use some help...
>
>My advice, for what it might be worth, would be to pursue opportunities
>to eliminate shock waves in *subsonic* applications, at least initially.
>Commercial airliners whose wings don't have to be swept back, propellers
>whose efficiency isn't limited by Mach effects at high tip speeds, etc.

One of the implications of this technology is that we can get rid of
(at least extreme) sweep for supersonic aircraft, resulting in much
improved takeoff/landing performance and reduced induced drag.  If it
works as promised, subsonic aircraft, at least for transport, will
probably be rendered as obsolete as propellor aircraft became in the
early sixties.

Propellors are a different problem, because we have to maintain zero
angle of attack.  That's probably not practical for a propellor,
because it corkscrews through the air by its nature.


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