World's lowest drag vehicle

[Ratliff]

going as fast as you can may not entail rocket science......

but going as fast as you "could" may very well entail rocket science.....!!!!

bak149 has it right, if anyone thinks for a second that I am a cubicle engineer they need to read the signature under my avatar.

I believe that we need both theory and testing.  From the practical side, guys like Willie are the best since they are unwilling to put up with theory that contradicts their experience while at the same time they are willing to accept theory that explains what they have felt and seen in real life.  We have to test.  If theory doesn't match reality, it is the theory that has to change.

BUT! Incomplete theory or messy interpretation of that theory often leads to messy data that only confuses the issue. We have to have clean data.  That means a clean interpretation of the theory and a clean test vs. a contrary theory.  There are some on this board who want to just keep pointing at history and old theory without adapting to modern experience.  I don't accept any combination of theory and data without some explanation of why they explain each other.

On the ALSR, I had many, many people shoving theories at us.  One of the best examples of what I spit at was one graduate student who said he had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number...

(if you're an aerodynamicist, you're laughing right now...)

His application to work on our program was accompanied by a statement that he had completed his doctoral thesis and was going to conduct experiments that proved his theory.

My dad would've boxed his ears for that.

Experiment tests theory, and nothing is completed or proven until it stands up to contrary (or "devil's advocate") testing.  That's what Bonneville is for.

Let's just remember that the salt is a dirty experimental environment.  Soft salt, wet salt, bumpy salt, hot, cold, wind, engine conditions, chassis tuning, got-to-make-a-run-now-because-if-I-don't-it's-next-year-itis, etc. etc. etc. all pollute the data.  There's a lot going on out there that pollutes the aero data.  Lots of people have read my posts here and believe that I can help them.  I'm flattered, and I even want to help as long as it doesn't cost me anything.

So tape some yarn to your lakester and send me the pictures.  You only have to go 60 MPH on a country road for most separation effects and causes to become apparent.  Blunt aft vehicle depend on organized separation and are a little harder to troubleshoot, but there are some good, simple rules to follow and some easy test methods to create stable recirculation behind a "Kamm" rear end.

Remember my motto:  Don't guess, TEST!

Some of that "history and old theory" is The Blue Flame got hit with a 40+ mph crosswind at over 600 mph and jumped sideways but didn't roll.

The modern experience is the Breedlove car rolled when hit by a 15 mph crosswind (although my hypothesis is a lot of that was due to Breedlove torquing the crap out of the car when he tried to regulate his acceleration by going in and out of burner).

[Ratliff]

Here's a couple of machines that although fully enclosed were among the last otherwise conventional bikes to hold the outright record.

[sockjohn]

As we now know a Dustbin is legal at the BUB..... racing under AMA/FIM rules on solo bikes....however, as per the rules the fairing has to be mounted above the axcle still leaving a good part of the front wheel exposed.................

Somebody correct me if I'm wrong, but their are also restrictions on the tail fairing (also discussed somewhere else on this forum), and that was what was required in addition to the dustbin to get to ~0.35 Cd.  The dustbin alone I thought only got down to around 0.4 to 0.45 Cd (which isn't too shabby!)

I was really mostly curious about what bikes were running 260mph, but interesting thread for sure.

I don't doubt that somebody in APS could do that well or better in terms of Cd (and even frontal area), but stock bodied Hayabusa to 300mph seems like it would take a lot more than "just a dustbin fairing" to get to 300mph, but I wouldn't be surprised to be proven wrong either.  There are certainly some impressive naked records getting set lately.

[Ratliff]

As we now know a Dustbin is legal at the BUB..... racing under AMA/FIM rules on solo bikes....however, as per the rules the fairing has to be mounted above the axcle still leaving a good part of the front wheel exposed.................

Somebody correct me if I'm wrong, but their are also restrictions on the tail fairing (also discussed somewhere else on this forum), and that was what was required in addition to the dustbin to get to ~0.35 Cd.  The dustbin alone I thought only got down to around 0.4 to 0.45 Cd (which isn't too shabby!)

I was really mostly curious about what bikes were running 260mph, but interesting thread for sure.

I don't doubt that somebody in APS could do that well or better in terms of Cd (and even frontal area), but stock bodied Hayabusa to 300mph seems like it would take a lot more than "just a dustbin fairing" to get to 300mph, but I wouldn't be surprised to be proven wrong either.  There are certainly some impressive naked records getting set lately.

The fastest vehicles at the Texas Mile and Maxton pavement land speed events are bikes (turbo Hayabusas). It turns out a bike can run as fast on one mile of pavement as it can on three miles of salt.

[ddahlgren]

Blue I have always had the feeling that directing the engine exhaust to fill in the low pressure behind a vehicle hard to test in a wind tunnel as it would need to be a rolling road that also had a chassis dyno so you run the engine WOT and generate the exhaust flow. So my question is there some way to do some baseline calcs on a CFD model that matches wind tunnel testing and add in X lbs per minute of air at Y airspeed and show what effects there might be. I would think the aircraft folks have this sort of tool. Next is there a way to predict the center of pressure movement vs relative speed? My concern is to predict if the CP will move forward as speed goes up and possibly go from stable to unstable.

On the enclosed chute tubes.. they scare me to death.. when and if a run is going bad and you need to slow down asap you are adding door deployment time to chute deployment time to actually slowing the thing down..
Dave

[Graham]

Hi all,

Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post. If I'm not, I'd love to talk to this guy whoever he is - sounds like he could really help me in my research, with his interesting theories!:

On the ALSR, I had many, many people shoving theories at us.  One of the best examples of what I spit at was one graduate student who said he had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number...

(if you're an aerodynamicist, you're laughing right now...)

His application to work on our program was accompanied by a statement that he had completed his doctoral thesis and was going to conduct experiments that proved his theory.

My dad would've boxed his ears for that.

I have never spoken to Mr. Ahlstrom, or his dad for that matter. My only attempt to establish contact with him, with a simple request for more information through Steve Fossett's PR man in 2007, was ignored, though evidently I have provided fodder for him if I have become worthy of making an example of!

I did not state that I had finished my PhD. I have not. I'd imagine it'd be quite hard to finish your thesis if you hadn't done any experiments...

I did not apply to work on his program. I have not ever said I had evidence that transonic objects created divergent pitching moment in ground effect regardless of alpha or Mach number.

I did say that I thought my work, some of which was on land speed record cars, including Breedlove's car, would be of interest to him, as it has been to a few others in the land speed racing community. Evidently it was not and I thought little more of it until now.

It is hard to know where Mr. Ahlstrom has been drawing his inferences from, then, although if you're anything like I apparently am, you could almost be tempted to come up with some more unproven theories: I wrote to Craig Breedlove around the same time, and in more detail about the early findings of my research, but once again a reply was not offered.

Perhaps Mr. Ahlstrom had also gotten his hands on a couple of presentations I gave at a symposium on shock waves, in Italy in 2006, in which I put forward some interesting undergraduate computational studies on the aerodynamics of Thrust SSC, as well as some of my own preliminary investigations into the aerodynamics of wings in transonic ground effect. This work preceded and informed an extensive wind tunnel program at the US Naval Academy in Annapolis, supported by the Royal Aeronautical Society.

Fortunately, neither of these fine institutions deemed it necessary to ‘box my ears’ at any stage.

Mind you, since then, much of my research has become publicly available in peer-reviewed journals - it'd surely have to be these formal results and discussions that caused Mr. Ahlstrom to scoff so decisively. The benefit of both reading and publishing in such journals is their insistence on rigorous validation of theories and models against reliable experimental results. In this way they ensure that they are not about to stake their reputation on substandard, unproven or incomplete work.

Given this, coupled with his adversity to personal contact, it would therefore make sense for Mr. Ahlstrom to address his issues with my research to the editors of these journals so that his criticisms can be properly put to a wider, interested and informed audience in an appropriate context 

[Blue]

Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post.

Yes, Graham, you are the graduate student I referred to.  I did not use your name to avoid a public confrontation, and you are welcome to contact me at my e-mail address or by PM; both of which you have access to since you have registered on this site.  I am only too happy to keep a dispute of technical theory private until someone challenges me in public.  Having exposed me to public criticism, you are now vulnerable to the same.  BTW, I publish too, am a guest lecturer, and write my own code; you could've found this out with a proper search.  This doesn't make my work (or yours) any more valid, it just means that it passed technical review and is worthy of discussion.

You were far from the worst example of "help" that was offered to us.  By far the worst was someone claiming to have the "secret" of using electromagnetic vehicle and exhaust plume charging to create a "gravity well" and an over-unity effect.  Your work stays within the limits of the second law of thermodynamics and was worth consideration.  I reviewed your e-mail to Craig, you never contacted me, so I do not understand where this "avoidance of contact" idea comes from.  In your e-mail, you postulated that your research with un-validated CFD "proved" that "shock waves" lifted the back of Sonic Arrow and caused the 1996 roll.  You were specific in your insistence that your TBD "test" would "prove" your theories. 

This is the basis for my dismissal of your attitude and work.

Whether or not you have accurately modeled transonic and low-supersonic objects and vehicles in intimate ground effect of a porous and plastic surface is not apparent from your research.  What is apparent is the following:

1. No known CFD solver has been validated for ground effect.
2. You are one of the few researchers exploring intimate the science of ground effect on transonic and low supersonic objects.
3. Your work does not account for decay of shock reflection via a variable density, variable porosity, and variable structure surface (welcome to playa, a VERY non-linear group of effects).  In addition, the explosive disassembly of the surface by the shock requires the surface ejecta to be included as significant to the model.
4. Your work does not account for the detailed mechanical and aerodynamic features of TSSC and Sonic Arrow 96.  For example, rolling tires, local surface alpha, suspension deflection, gross vehicle alpha (controlled vs. actual), louvers and negative Cmu on TSSC, aft separation and its effects on transition to terminal shock and stagnation, etc.  These are major, not minor effects for shock formation and decay, as well as all pitching moment, stability and control effects.  FYI, no models or drawings exist of SA-'96.  The die cast model is ~95% accurate for SA-'97 and less than 60% accurate for Fossett LSR-'08.
5. At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature.  The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8!  Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground.  This increased the strength of the the upper surface shock.  Tehrefore, there is a downforce based roll component, but not a lifting force based roll component.  Did you account for any of this?
6. Like many proponents of the flat-bottom cars (I'm not saying you're one), you made no distinction in your e-mail between blunt-fat vehicles like TSSC and high fineness ratio vehicles like Sonic Arrow.  Strength of a compression wave is proportional to the first and second order of displacement:  max cross section and fineness ratio.  This is linear wave drag theory that I am sure you are familiar with.

It is for these and other reasons that Dr. Hal Ahlstrom and myself believe that CFD is not useful in this instance.  In fact, it is detrimental, in that it will create a vast volume of questionable data that will probably lead in the wrong direction due to its volume.  A better course would have been to ask us if we could add some aerodynamic sensing to our data collection along with detailed 3D vehicle coordinates so that you could validate your modeling with our data.  As you embark on your career in aerodynamics, try to remember that it's not real until it's tested.

Don't guess, TEST!

and this doesn't mean CFD.

[Ratliff]

Of course, it’s an unproven theory, but I suspect that I am the "graduate student" that Mr "Blue" Ahlstrom wrote about in the following post.

Yes, Graham, you are the graduate student I referred to.  I did not use your name to avoid a public confrontation, and you are welcome to contact me at my e-mail address or by PM; both of which you have access to since you have registered on this site.  I am only too happy to keep a dispute of technical theory private until someone challenges me in public.  Having exposed me to public criticism, you are now vulnerable to the same.  BTW, I publish too, am a guest lecturer, and write my own code; you could've found this out with a proper search.  This doesn't make my work (or yours) any more valid, it just means that it passed technical review and is worthy of discussion.

You were far from the worst example of "help" that was offered to us.  By far the worst was someone claiming to have the "secret" of using electromagnetic vehicle and exhaust plume charging to create a "gravity well" and an over-unity effect.  Your work stays within the limits of the second law of thermodynamics and was worth consideration.  I reviewed your e-mail to Craig, you never contacted me, so I do not understand where this "avoidance of contact" idea comes from.  In your e-mail, you postulated that your research with un-validated CFD "proved" that "shock waves" lifted the back of Sonic Arrow and caused the 1996 roll.  You were specific in your insistence that your TBD "test" would "prove" your theories. 

This is the basis for my dismissal of your attitude and work.

Whether or not you have accurately modeled transonic and low-supersonic objects and vehicles in intimate ground effect of a porous and plastic surface is not apparent from your research.  What is apparent is the following:

1. No known CFD solver has been validated for ground effect.
2. You are one of the few researchers exploring intimate the science of ground effect on transonic and low supersonic objects.
3. Your work does not account for decay of shock reflection via a variable density, variable porosity, and variable structure surface (welcome to playa, a VERY non-linear group of effects).  In addition, the explosive disassembly of the surface by the shock requires the surface ejecta to be included as significant to the model.
4. Your work does not account for the detailed mechanical and aerodynamic features of TSSC and Sonic Arrow 96.  For example, rolling tires, local surface alpha, suspension deflection, gross vehicle alpha (controlled vs. actual), louvers and negative Cmu on TSSC, aft separation and its effects on transition to terminal shock and stagnation, etc.  These are major, not minor effects for shock formation and decay, as well as all pitching moment, stability and control effects.  FYI, no models or drawings exist of SA-'96.  The die cast model is ~95% accurate for SA-'97 and less than 60% accurate for Fossett LSR-'08.
5. At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature.  The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8!  Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground.  This increased the strength of the the upper surface shock.  Tehrefore, there is a downforce based roll component, but not a lifting force based roll component.  Did you account for any of this?
6. Like many proponents of the flat-bottom cars (I'm not saying you're one), you made no distinction in your e-mail between blunt-fat vehicles like TSSC and high fineness ratio vehicles like Sonic Arrow.  Strength of a compression wave is proportional to the first and second order of displacement:  max cross section and fineness ratio.  This is linear wave drag theory that I am sure you are familiar with.

It is for these and other reasons that Dr. Hal Ahlstrom and myself believe that CFD is not useful in this instance.  In fact, it is detrimental, in that it will create a vast volume of questionable data that will probably lead in the wrong direction due to its volume.  A better course would have been to ask us if we could add some aerodynamic sensing to our data collection along with detailed 3D vehicle coordinates so that you could validate your modeling with our data.  As you embark on your career in aerodynamics, try to remember that it's not real until it's tested.

Don't guess, TEST!

and this doesn't mean CFD.

"At the speed of the 1996 roll, the car was only traveling at 675 mph, or ~M.89 for the temperature.  The leading edge sweep of the struts is 75 degrees and would not create a compression wave until M3.8!  Yes, the root interface and the un-sweep at the strut to wheel fairing interface would create a shock, but Breedlove had cambered the leading edge down so that the lower surface achieved a negative alpha so no shock was present between the interface and the ground.  This increased the strength of the the upper surface shock.  Tehrefore, there is a downforce based roll component, but not a lifting force based roll component.  Did you account for any of this?"

This does not conflict with my previously stated hypothesis that the car rolled because Breedlove going in and out of burner trying to regulate acceleration was torquing the crap out of it.

However, Dr. T. P. Torda changed The Blue Flame from stub wings to open struts not because the wind tunnel tests (performed at Ohio State under the direction of Dr. J.D. Lee) were indicating the stub wings generated compression waves, but because the tests indicated the interaction of vortices coming off the nose with the stub wings created rear end lift.

On the other hand, it is good to know my proposed use from 1983 of swept wings to support outboard jet engines on the front of a vehicle (see link below) could be correct in principle.

http://www.landracing.com/forum/index.php/topic,4108.0.html

[sheribuchta]

graham--i learned at a very early age never to snitch on anyone     ESPECIALLY YOURSELF   


                           willie buchta

[Graham]

HAha, thanks Willie Buchta, but I don't feel like I "snitched" on myself. I'm not in hiding 

You will notice that I have not rubbished anything Mr Ahlstrom has said relating to his thoughts or findings as he has done with what he knows of my work, unproven or otherwise - despite the forum name, I did not come here for a technical discussion, much less some sort of flame-war. I took issue with his false statements regarding me personally, and I think I set those straight in my original post. Although I was not named publicly, I felt the need to address the numerous inaccurate statements that referred to me, lest we all have to read through the forum rules again.

I stand by what I wrote to Craig Breedlove, although I in no way sought to lecture him and had hoped for a proper discussion I could learn from, and I've definitely learned... my lesson about discussing work in its early stages. At the time it seemed more urgent in that the car looked like it was going to run again soon and I wanted to find out as much as possible. In the end I could find out no more about the wing profiles, and certainly did not know enough detail to make some results public. I do not believe one single other person has actually seen any of that work of mine, yet it appears to have generated a lot of discussion.

I didn't mean to step on anyone's toes by forwarding my own thoughts to Craig Breedlove based on my experience to that date. I do not wish to be involved in an argument on a web forum.

I did not then claim to be right or have all the "answers", and I never would. My research speaks for itself and I would again refer criticisms of my work to the journals which have reviewed it, and published it as reliable, so that those comments are subject to the same level of review as my work was. I am always interested to read about conflicting or supporting research.

Eric, Stuart Radnofsky assured me he had contacted you on my behalf. If he did not, then I apologise for assuming you didn't wish engage in a discussion at that time. If there was misunderstanding, please do not treat my letter to Craig as an application to join your project or a statement of completion of my thesis. I also have no interest in modeling your revised car, your work is your own and I have no intention of pestering you with my thoughts on the matter or creating, as you rightly put it, a vast volume of questionable data.

With regards to the presentations I gather you have seen - one was not my own work, although I by-and-large support the findings and certainly deemed them to be worthy of closer investigation. The other was an absolutely preliminary CFD study. The nature of the symposia was designed to allow researchers to discuss such work and recieve valuable feedback, which I did. If I had thought these results were in any way worth publishing, I would have done so. We do not watch the rough first cuts of movies, but sometimes our interest is piqued by the teaser trailers.

Many CFD solvers have very accurately modeled ground effect aerodynamics for a variety of applications, but you are more than entitled to your own opinions on their appropriate uses. I'm well aware of the limitations of computer models.

At any rate, I'm not designing or building jet cars and even then I'd just be clogging up a message board which is useful for many others, so I wish you all the best in your tests.

Graham

[Ratliff]

As long as we're discussing supersonic cars, something I think would be worth revisiting is the issue of whether the results below represent the minimum size required for a supersonic steam rocket car or if it might be feasible to go smaller.

http://www.landracing.com/forum/index.php/topic,4008.0.html

Waldo Stakes ( www.sonicwind.com ) has long believed his tiny "Sonic Wind" rocket ice sled could go supersonic given perfect conditions.

A few weeks ago I got curious about how fast a 4 inch diameter turbocharger rotor would be going at 80,000 rpm if it were a wheel on a car. When I did the math it worked out to around 900 mph.

So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.

[tortoise]

So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.

With those very small wheels, you wouldn't, I would think, be able to run a lot of static downforce, so you'd need a body design which would have stable lift/downforce characteristics under varying conditions. No movable aerodynamic surfaces allowed, right?

Leave me off your list of potential drivers.

[Ratliff]

So putting the concept of ultrasmall wheels together with Waldo's concept of an ultralight rocket I'm now wondering whether a supersonic LSR car with a dry weight of under 1,000 lbs might be feasible.

With those very small wheels, you wouldn't, I would think, be able to run a lot of static downforce, so you'd need a body design which would have stable lift/downforce characteristics under varying conditions. No movable aerodynamic surfaces allowed, right?

Leave me off your list of potential drivers.

It's Formula One and the rest of those Euro wussies that started the trend of not allowing movable aero devices (although F1 is changing that either next season or the season thereafter).

However, movable aero has always been legal in land speed. In 1962, Art Arfons set an SCTA record of 338 mph with movable aero. In 1964 and 1965, Arfons set the FIA record three times with movable aero. Arfons also used movable aero on the land speed car he ran in 1990 and 1991.

Who says a car only need four wheels? For ultrasmall wheels on a land speed car, I envision modules like asphalt racing skis except with titanium wheels and brake calipers on the frames that use the wheels as brake disks. The wheel bearings would be lubricated with a pressure fed oil system like a turbocharger.

[PorkPie]

Eric,

just a information to the SoA Sonic Arrow models.

From the 96 version was three very accurate models by Arthur Russell of LA. in 1:12 scale

One was given to a sponsor, one was modified (in the Rio Vista workshop) at first into the 97 and than into the 2000 version, which was never complete released into the real car. The modification was done by Decal Dave, a very talented artist - he was also in the team which built the original car and he done the alignment of the racer in 98/99, after they found out that the frame was bend in 96.

The third model is in parts still by Arthur Russell.

I got picture from the 96, 97 and 2000 version.

Craig Breedlove gave the 2000 version to Steve Fossett - it was on the plane when he was 2006 at Bonneville.

You be right when you write that the 1:43 scale model is not 100 % correct - but for a China model and a record breaker model it is not bad.

Also, Arthur Russell done a 1:43 scale model of the 96 version - but he done only the master, he never produced some models with this master. The "outrigger" would be very critical to do them in resin.

[Ratliff]

Fascinating subject - wonder if Mr Reynolds and his number enters into projecting the bike's performance into 440plus mph?

Remarkably, the record holding Varna bicycle bears a more than passing resemblance to the eforts by NSU with motorcycles in the '50s.

 Taking things a step farther, does this skateboard racer attached ready to race DOWN Shell Hill @ Signal Hill (Long Beach, Ca)  in '78resemble Jack costella's latest two wheel efforts?

Nothing new under the sun!

Even that was not the first time.