 Okay, first of all, why don't we start by you giving just a brief description of what laminar flow is? It's an interesting question to give a brief description. In essence, what we're trying to do is control the boundary layer so that it looks a lot like in a simple minded way would be if you looked at a car that was in a smoke tunnel and you see the commercials on TV and you see the smoke waves going over the car and they're nice and smooth and then later on they burst and they become a big bubble. The laminar flow part is a place where they're smooth, where the air actually flows over the wing in a very smooth manner in a low drag configuration in a more efficient way. All airfoils have some laminar and have some turbulent flow on them. In the area where it's laminar, it's basically the more efficient portion of the airfoil. Another common phenomenon that people can relate to laminar flow would be a cigarette smoke. It's the portion of the cigarette smoke that comes off of the cigarette real straight and smooth and tightly wound and then later on it bursts and there's this big smoke spot in the middle of or smoke ball in the middle of off of the cigarette. That's the turbulent section. The straight piece is where the laminar flow is. So it's the tightly wound, well organized, smooth airflow that you're talking about when you say laminar versus turbulent. You just mentioned something and that was the phenomenon. What are specific phenomena that are associated laminar flow phenomena that are associated with supersonic flight but not with subsonic flight? Well, probably the biggest difference in supersonic laminar flow is that is the airfoils and the wings tend to be more highly swept in that the leading edges are, you know, in the order of 35 to 70 degrees swept back from a 90 degree angle. And typically a subsonic laminar flow airfoil doesn't have quite that much sweep. And the sweep actually makes the airfoil, makes it more difficult to maintain laminar flow because you have a component of inbound air or an air molecule that's coming towards the swept wing. Part of it goes straight back, but part of it goes out towards the wing tip and that's called cross flow. And cross flow is the phenomenon that makes supersonic laminar flow. It was one of the phenomenon that makes supersonic laminar flow more difficult to maintain than subsonic laminar flow. It's much more, much more a larger forcing function if you will for supersonic laminar flow than it is for subsonic laminar flow. There's also another concern and it has to do with the size of a leading edge radius and the fact that the attachment line or the place where the pressure actually separate, the molecules actually separate. Some go over the top, some go over the bottom. That area would be called the stagnation point or the whole line of those would be called the attachment line. And that attachment line controlling exactly where that is on a swept wing and a supersonic wing is a little bit more difficult than it is necessarily on a subsonic wing. Again, supersonic wings tend to be swept highly making it much more difficult to control exactly where the attachment line occurs. So those are the two things that make it more difficult. The pressure distribution itself is a lot more difficult to maintain in order to maintain it in a pressure distribution conducive to laminar flow. You actually have to shape the airfoil properly and the shaping of that airfoil is part of the art and that's of learning how to make supersonic laminar flow work. And it turns out that it needs some augmentation. Subsonic laminar flow can occur or does occur easily, relatively easily in the natural state. You can actually maintain subsonic laminar flow back to fairly high percentage cores, 35, 40 percent quart. There have been a number of experiments where we've done that, flight experiments where we've done that and they've been wind tunnel experiments with them. Supersonically, there hadn't been very much research in it. It's we know that we can get laminar flow to an inch or so back. Now we're trying to maintain it further aft and in order to maintain laminar flow further aft we have to come up with some method of augmentation and that's why we're using suction to actually pull the boundary layer in essence, pull the boundary layer back down and re-laminarize the boundary layer and hopefully we can maintain a pressure distribution by augmenting with suction to keep laminar flow extending further and further aft along a wing surface and obviously if you maintain laminar flow for a larger distance you can reduce the drag of an airfoil and if you can reduce the drag you can increase your fuel efficiency, if you can increase your fuel efficiency, you can increase your payload capability and you know it's just a whole raft of things that come out of being able to maintain laminar flow. You just mentioned the fact that you're trying to get it back a little further, back a little further and back a little further. Does that relate to the different phases that are in the research that you're doing? Indirectly, yes. What we have done thus far with one of the F-16 XL number one which was a cooperative experiment with Rockwell International North American aircraft Rockwell and NASA Langley and NASA Dryden and to a limited extent actually NASA Ames was also involved in some of the computational work that went along with this. We have demonstrated that you can maintain laminar flow back to roughly 25 percent cord, it's under certain conditions. The next experiment that we plan for the second airplane is to maintain laminar flow further aft back as far as 50 to 60 percent cord. So yes, we are doing it stepwise. The first experiment showed us that it was in fact achievable and in fact it might be a little easier in certain areas to do than we anticipated. The real world tends to be a little bit more forgiving, it appears you know from a flight perspective the real world is more forgiving than the computational or the theoretical world says it should be. But we haven't gotten enough of an understanding as to exactly why we're able to do what we're doing. We know we can do it. Now we have to try to figure out exactly what is the phenomenon that we're actually able to control to make us get laminar flow to 25 percent cord. Meanwhile we want to extend that yes back to 50 or 60 percent cord which is a big driver in the design process for the high-speed civil transport airplane. If we can achieve laminar flow that far back we have actually correlated unit Reynolds numbers to a large enough number that the theoretical people and the designers for the high-speed civil transport have a lot of confidence that when they scale this up to the full-size vehicle the scaling will actually be fairly accurate. But on the high-speed civil transport they may not have laminar flow back to 50 or 60 percent cord but if we can achieve it to 50 to 60 percent cord now we know we understand the phenomenon well enough to be able to use it to our advantage on a high-speed civil transport. Primary driver is that it has a configuration that is close to the configuration that the high-speed civil transport is right now on the on the table it looks like it's going to look like. It's a very small airplane but it has a 70 degree swept wing and the high-speed civil transport designs right now appear that the wing is going to be roughly a 70 degree sweep. The cord is not long enough it's but it was an airplane that was available with the right sweep angle for test section and so that appeared to be the right place to start. It's the only one of the few airplanes that are available right now to do that type of work and that's the other reason why the airplane was selected it was actually available. Back in 85 the Air Force and General Dynamics parked the airplanes and said they had no more use for the airplane and in 88 NASA thought that they could use an airplane and meanwhile the Air Force was looking for somebody to either take it off their hands or to or the Air Force was going to destroy the airplane so we said we've got a use for it we'd like to have the airplane. The airplanes are actually loaned to us they don't belong to NASA they belong to the Air Force and they're just on loan to the to NASA for the duration of the flight experiment. When you are conducting a flight experiment what measurements are you trying to obtain? Well we actually collect on the order of 250 to 300 pieces of data telemetered to the ground we display to our engineers somewhere in the order of about 150. Among the parameters we're displaying to our engineers are the pressures coefficients of pressure it's actually the pressure is measured and then we run it through a computer to display in a pressure distribution format what the pressure distribution looks like. We also measure and display to our engineers whether the flow is laminar or turbulent and we use a thing called a device called a hot film anemometer or hot film sensor which in essence is a piece of a a strain gauge bridge and by the way it's manipulated and and conditioned the signal is conditioned we can actually tell whether we have laminar or turbulent flow at a at a specific discrete location along the wing where these things are located. Those are the two primary pieces of information that we collect we also collect data on the suction levels how much suction are we does it require to maintain the laminar flow at those under those various conditions and of course the conditions themselves are recorded whether what our mock at mock altitude airspeed angle of attack angle of side slip all of those are recorded in telemetered to the ground so that the researchers can tell whether or not we are on the conditions that we need to examine whether or not laminar flow occurs then. What do you learn people that are doing wind tunnel testing you know I know they tested some flat plates and in a quiet tunnel they're testing you know that that was the first three to four percent simulation what do you learn from them that helps you in what you're doing. Most of what they have done thus far they're they're the beginning of the experiment they're the ones that say well if you can shape your airfoil this way if you can if you can build a contour if you can build an experiment that looks like this you are most likely going to be able to get through the hardest part of the region the hardest part of the experiment which is to get the leading edge to be laminar if you can maintain laminar at the leading edge the rest of it will probably fall out you may have to manipulate your experiment just a little bit but the the further on will follow. So what we really get out of them is verification of some of the theories that the design theories for our experiment so the design starts whether it's in a lot of times that is the computational fluid dynamics people start working on what they think is a good design then they might fly a small experiment in one of the tunnels and when they think they have something that really is does show promise then we'll scale it up to an airplane and do a flight experiment which will be the in-flight validation of what the wind tunnel said and what the computational fluid dynamics work said. Oftentimes we don't get 100% correlation in the in the data what we get is some differences in terms of what we get for real time or flight data and we take that turn it back into the computational fluid dynamics folks or to the wind tunnel people and say well our data shows this but our configuration looks like this why don't you run it again put it through your tunnel again or put it through your code and see whether or not you can figure out what the difference is between what we got and what you got in terms of results. So there's not always 100% correlation but we use this as an iterative process. Oftentimes they don't get the same answers we get and they're convinced that their part is exactly right so we have to go back and find out what it is and our our piece of the experiment that might be different so it's you know it takes a lot of communication a lot of talking between the computational fluid dynamics people and the wind tunnel people and the flight experiment people and the applications people and the instrumentation people everybody has to talk to everybody in order to make sure that we really are doing the experiment we all think we're doing and and we have had on occasion some differences of opinion in terms of what we are doing and what we think we're doing and what somebody else thinks we're doing so it it does it's a difficult process to keep iterating everybody's data until we get correlation. Just to digress from that one of the things that I told Lou Williams is that I was going to make a point of being really fair and objective because obviously when I talk to somebody who's doing CFD oh their work is what is most important and then if I talk to somebody doing wind tunnel experiments well those computer wings they don't know what they're doing and what I said I told them that's a positive thing because that person is very enthusiastic about what they're doing and that's where their heart is but what I see is that in order to get a vehicle built and off the ground it's going to be CFD wind tunnel and flight experiments there's no way that one of those is more important than the other but it's really funny to talk to somebody. Do you know who Bernie Spencer is by any chance? I know the name but I don't know him personally. He's a wind tunnel guy and he did a lot of testing for the shuttle and I had to interview him last year about the HL 20 and he was so funny because he kept talking about the computer weenies the whole time and I had him on tape and he called and I said we're gonna have to rephrase that a little bit Bernie we can't call him weenies and he's just you know anyway. It's I mean it is a that's a tough problem you know the and we have you know we have our growing pains trying to correlate a you know make a flight experiment add the most value to an overall program like this because everybody does have their empire if you will and everybody wants to make sure that their piece gets gets added into the equation. Flight is an important part of the validation process and especially when you're dealing with a phenomenon that we don't understand yet. There are some kinds of technologies that can be done you know computationally or in the wind tunnels but I think we're in an area now where we don't know enough and we need some flight data to correlate with and I think overall the program does recognize that and everybody involved in the program recognizes that but flight is also very expensive and that's that's a real drawback anytime anybody looks at trying to do a flight experiment they say oh my we're gonna spend millions of dollars doing this flight experiment and we could do the same experiment in a wind tunnel or in a computational world for considerably less and convincing everybody that you still need the flight data is sometimes difficult you know so when you talk about your computational people or your wind tunnel people and you talk about your air applications people your flight applications people getting a meeting of the minds is the hardest thing you know getting everybody to say yes this is the very important thing for us to do is really difficult and it hasn't been flawless so far in this program although we're getting better we're we're definitely working hard harder to make sure we're all part of the big piece of the piece of the program and I think it's starting to show to date how has the applications portion how has that been validating the other stuff what's the success well we have we've collected sufficient amount of laminar flow or laminar turbulent transition data and a significant amount of pressure distribution data to be able to show that with minor anomalies we can we cannot we do understand how the pressure distribution is has been developed you know there are some things in the pressure distribution we don't understand but we're beginning to believe that some of that's our instrumentation measurement technique rather than it has anything to do with the phenomenon called supersonic laminar flow which is good I mean it's what it's done for us is it's it's improved our instrumentation technique capability as well which will make the next experiment a better experiment in transition where transition location occurs we have been able to show that the codes that that developed that this airfoil shape was developed by are not a hundred percent representative of what really happens in the real world but they're close enough there's some things that some phenomenon that they didn't anticipate in the code development that need to be revisited it's on it's fair to say we did not predict the results we got you know the computational fluid dynamics and the wind tunnel results did not predict the results we got on the first part of the ship one experiment but they predicted enough of of the information in a satisfactory manner that we now have something to to do some checks and balances against as I said earlier now is time for the CFD folks and for the wind tunnel folks to go back and look at the differences between what they thought we were going to flight test and what we flight tested and see whether or not they can we can start correlating the differences between the two most importantly I think the the flight experiment has shown that yes you can get laminar flow and it's not as may not be as difficult to do under these circumstances as we anticipated it would I mean there's a lot of a lot of apprehension that we were going to have to do a lot of provide a lot of suction for example in order to maintain laminar flow and we're not providing all that extraordinary a really large amount we're definitely providing suction but the amount is not as much as people predicted it would be so we are starting to show you know that that this is a handleable problem it's not out of our out of our capability which is a very big confidence builder that we can get from here to there without you know without having to go over the impossible you know the impossible ridge first so basically what we've done so far is just provide the data to validate what we've done so you know what the theoretical people have done so far and that and that gives them the step the confidence step they need that they can go the next you know they can go to the next level of complexity and start understanding a little bit more about you know the differences the difference between cross flow and you know the e to the n factor is computational results and those kinds of those kinds of computational theories that they're using they're getting enough data to validate that the theories are valid theories they just need they need to be tweaked up and tuned up just a little bit more how does the what you need for laminar flow control and what you're finding to achieve the best possible results how is that eventually going to affect what they need in sonic in sonic boom area or in the high lift area or their needs are obviously a little different yeah their needs are different and in fact the integration of laminar flow high lift sonic boom or shaping is going to be a very difficult task because they don't meet those those at least those three phenomenon don't meet at the same place so it's going to be a compromise everybody is going to have to say through whatever whatever validation testing they do I can tolerate this much detriment to my best performance condition and still get some gain it's it's the added value added equation really more than anything else it's if I have some laminar flow under certain circumstances but I give it up during the the approach and landing phase or the takeoff phase if I have a sonic boom but it's not as offensive as a very sharp sonic boom and if I have you know a noise footprint from the high you know because of the high lift phenomenon that's half of what you know it meets the far criteria but it's not not as good as I really want it that whole compromise and that whole integration issue has not really been addressed yet it's everybody recognizes we're going to have to compromise high lift and and supersonic laminar flow are almost mutually exclusive for certain parts of a flight regime but you don't need supersonic laminar flow when you're subsonic so maybe it's not that big a deal you know maybe we can work around that one and I so I think that that we have to understand the conditions where supersonic laminar flow occurs we have to understand the conditions for getting good high lift performance characteristics and then once we understand both of those we can integrate the requirements for both in such a way that we don't destroy you know 75 percent of the capability in either case the worst thing you could have is a poorly integrated airplane one that does everything poorly what we're hoping for is an airplane that has all the technologies put together in such a way that we've maximized you know all of parameters at the same time and you're not going to get a hundred percent of any other and ultimately what what are you aside from the test measurements what once all the test test measurements have been done what do you feel like the purpose of all your research database is going to be the database will probably be used for years to come to validate it'd be be a lot of test case data to validate development of new computational codes and and theoretical codes the area we're dabbling in now supersonic laminar flow is an area that is is brand new you know there was some experiments done in in years gone by there's some x21 criteria that people believe in there's some work that was done on a 104 you know back in the I guess it was the early 60s those two experiments were enough to set establish some criteria for whether or not supersonic laminar flow is or laminar flow and supersonic laminar flow were achievable what we have done and what we will be doing through the XL experiment besides validating some of the codes that the high-speed civil transport is going to use for design methodology we will actually fill the database that will allow researchers for future generation airplanes augment the designs in other ways not just for the point design called the high-speed civil transport but perhaps for some other vehicles some other more focused more highly specialized vehicle that could take advantage of an airfoil or a pressure distribution development for another region of flight that maybe we haven't thought too much about to date so the database by itself is is going to be valuable to everybody it's certainly designed to help the high-speed civil transport but to understand the phenomenon transition physics and and you know attachment line phenomenon and that type of thing that's the importance that's some of the important data that will come out of this I mean we've played we've been in the laminar flow business for well if you read some of the some accounts we've been in laminar flow since beginning of NASA or NACA actually there was some laminar flow work done in the begin during the NACA days I personally have been in the laminar flow business since 1979 and it's been subsonic laminar flow up till now and there's always new things to look at there's always the effect of once you you know you take a unknown configuration now you start varying very in the parameters instead of having 70 degrees sweep let's look at the effect of 75 degrees sweep instead of having maximum suction let's look at less suction instead of having two degrees angle of attack let's look at you know three degrees or one degree angle of attack there's a whole raft of parameters there that that when you're when you're focused on a vehicle that has a certain flight regime you tend to only look within that window and we'll collect enough data that you can look at the effect of changing the various parameters um and use that to validate other codes for other flight vehicles now the f-16 currently isn't flying it's it's hangered right both f-16 xl airplanes are hangered right now although friday we'll be flying the first airplane again so and is that are you starting a a different round of experiments xl ship ship one which is the one that we started the nasa rockwell north american aircraft experiment with is going into a phase we'll call it a phase two experimentation where we are actually trying to document collect significantly more data on the suction requirements for laminar flow phase one was basically can we can we achieve laminar flow back to you know 25 or 30 chord phase two is understand the the suction distribution that's required to do that so yes the ship one is in a second phase where we're collecting another set of data when that's complete the airplane in fact will be turned back to transferred back to nasa langley where they will begin the high lift experiment where they will actually start looking into the configuration requirements for high lift for the supersonic or high speed civil transport and dryden and langley will be working together on that experiment with langley being the lead most of the flight activity occurring back at langley and modification activity occurring there we will provide the support as necessary to get that airplane in the air back there the second airplane ship two is the centerpiece of the laminar flow control phase of the high speed research program and that airplane currently is configured with a passive glove which is no suction at all it's just a foam and fiberglass glove on the right wing and with that we'll be examining attachment line criteria pressure distribution verification since they predicted that they designed the shape based on on codes and we're going to go out and see if that shape really is providing the pressure distribution we had hoped for transition data whereas laminar flow occurring on a passive surface that's shaped to be conducive to laminar flow in a supersonic flight environment and that's that's probably a four to six month flight program that we have planned there and at the term at the completion of that flight program that airplane will go back into modification for the installation of the big experiment if you will and that's the one where we'll be putting a glove suction glove on the airplane it'll go on the left wing of the airplane it'll be it'll go roughly back to 50 or 60 chord and that one will use suction to try to maintain laminar flow that far back these gloves are basically almost full span for the 70 degree swept portion of the wing the wing is the airplane's claim to fame is it's the cranked arrow it's got a 70 degree swept portion and then it bends oh three quarters of the way out to the wingtip it bends to a 50 degree sweep and the section inboard of the 50 degree sweep is where we put all of the experiments because that's where our 70 degrees is so the second airplane will be a very busy airplane it's we're hoping to collect the entire database for the high-speed civil transport laminar flow control effort by the end of fiscal year 95 and of course we don't have the glove on the airplane yet so you know we've got a lot of work ahead of us to try to get it all done it is on it is on and in fact we're hoping to to have the first flight for that that airplane in that configuration before the before the end of august and we're hopeful that it'll actually be the first or second week of august that will actually get the first flight with that glove on when you when you do the the suction experiments on one and you're going through different iterations for the amount of suction that you need what do you do you fill up the holes i mean it's a stupid question no the the glove itself is a porous the skin is porous it's a piece of titanium sheet that has 2,500 holes per square inch laser drilled holes per square inch and then beneath that is a a corrugated substructure and it's we call it flutes and basically what it looks like is a piece of cardboard if you will if you look at the cardboard core corrugations that's basically what's underneath and we suck the air span wise using a suction pump that's located in the fuselage of the airplane we suck the air through the hole the porous holes span wise and then in this case we're just dumping it overboard because we have no use for it in a high speed civil transport there may be some use for that air somewhere else but in this case we're not worried about total integration we're just worried about determining laminar flow requirements so when we regulate the suction level what we really do is reduce the suction pump pumping capability now we haven't done any of that yet all we're trying to do is document how much suction we have right now for the results we've gotten right now we have a fast-paced program here that we may delete some of the some of the nice to have objectives and one of those things is to look at the effect of changing the suction level and we may run out of time to be able to do that in which case we'll get that data on the next experiment that'll go on the second airplane