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April 25, 2000
QuestChat with Steve Smith

Aerospace Research Engineer
NASA Ames Research Center, Moffett Field, CA



[ Sandy/NASAChatHost - 2 - 05:40:47 ]
Hello! Today's Aerospace Team Online QuestChat with aerospace research engineer Steve Smith will begin at 10 am, PDT (1 pm, EDT). Be sure to check out Steve's bio BEFORE coming to the chat room: http://quest.arc.nasa.gov/aero/team/smith.html -- We look forward to chatting with you!

[ Sandy/NASAChatHost - 7 - 09:09:29 ]
RE: [Sue] Hi Sandy! We're logging on to make sure we've got a good connection. We're looking forward to today's chat. I've got 12 middle school students studying aeronautics with me today.
Hi Sue! Looks like you've got a good connection right now! We are really looking forward to chatting with you and your 12 students today :-) "See you" in about 45 minutes...

[ SteveSmith/ARC - 8 - 09:30:58 ]
Hi Everyone!

[ Sue - 9 - 09:38:34 ]
Hi Steve!

[ Sandy/NASAChatHost - 11 - 09:47:12 ]
EVERYONE: I am holding all of your questions in my "moderator's chat room" until the chat officially begins in about 10 minutes. You won't see them until I post them so you don't need to keep resending them.

[ Sandy/NASAChatHost - 12 - 10:02:54 ]
Ok Everyone, Steve is here and ready to take your questions :-)

[ SteveSmith/ARC - 15 - 10:05:30 ]
RE: [Cindy] I read in your bio that you are building your own powered airplane. What will the finished product be like?
HI Cindy, Well, its a 2-seat airplane, with a low wing, and its what we call a tail-dragger: it has two main landing gear and a tail wheel. the seating arrangment is tandem, front and back seats. It has a 25-foot wingspan, and it will have a maximum weight of 1850 lbs.

[ SteveSmith/ARC - 16 - 10:07:01 ]
RE: [Njuguna] Hallo Steve, Being a little bit more specific, IF you were planning a helicopter blade design project including testing in the wind tunnel, what budget would you work with, an approximation. Thanks!
Well, it depends on if you just want to test a blade section, or a complete rotor system. A simple blade test might cost about $100,000, but a full rotor test could cost several million dollars!

[ SteveSmith/ARC - 20 - 10:13:29 ]
RE: [Sue] Tell us more about wing design. We know that you have researched some advanced wing designs. We're building gliders, and the kids have been experimenting with various shapes. What shape do you think offers the most promise?
There are classical theoretical results that show that an elliptical wing planform is best. Modern refinements show that a good wing planform is to have a half-ellipse with the trailing edge straight. This shape gives the best spanwise distribution of lift. Of course not many "real" airplanes are built that way, because it is expensive to build a curved planform shape, and for most purposes, a straight, tapered wing works almost as well. But for hand-launch gliders, the half elipse really works well.

[ SteveSmith/ARC - 21 - 10:16:13 ]
RE: [Sue] Followup question about wing design: What works better, wings that encompass the entire fuselage, or wings more like the standard commercial design? Which gives the longest glide time? How necessary are rudders?
I'm not sure what you mean by "encompass the fuselage" please explain. The vertical fin, (which the rudder is a moving control surface on) is really important for directional stability, so if gusts or turbulence hits the airplane, it will always straighten out and fly straight ahead. The rudder is a control for yawing, to help turn the airplane, in combination with the aileron controls on the wing, which are roll controls. The pilot uses the rudder and the ailerons together to make a smooth banking turn.

[ SteveSmith/ARC - 23 - 10:19:44 ]
RE: [Njuguna] Hallo Steve, Waht is you biggest challenge in you career and what would you advice an aspiring aeronautical engineer outside the USA who fancy Nasa?
Wow, thats a hard question! I guess my biggest technical challenge was to do all the research to finish my PhD degree while also working on regular projects. But there are other kinds of challenges at work - things like getting ideas for projects approved. Sometimes the research that I think is important is not what the leaders want us to do. So I have to find things that are within the research areas we are supposed to focus on. This is frustrating and challenging. Aeronautics research isn't very well funded right now, so its hard to give advise about being an aeronautica engineer. The best we hope for is that the business cycles will come around again, and aeronautics research will be better funded.

[ SteveSmith/ARC - 26 - 10:22:44 ]
RE: [Sarang] Hello Sir,first i would like to ask you is that besides the Einstein's equation ,why it is not possible practically to build a spacecraft that will exceed or equate the speed of light?
Hmmm, this is not a field I'm an expert on, but I know that according to modern theory, objects that go very fast, almost to the speed of light, seem to act as if they are heavier, so it takes more and more power. In the limit, at the speed of light, it takes infinite power because the object acts infinately heavy. So, the only things that can go the speed of light are actually weightless - they have zero mass.....

[ SteveSmith/ARC - 29 - 10:29:30 ]
RE: [Sue] The kids want to know: What do you think careers in aeronautics will look like in the future? How do you envision them changing?
WEll, as I said to Njuguna, I hope the business cycles come around and there is better funding for research. I think there will be two big changes in the way aeronautical research works in the future. 1st, on the way we work...computers are still getting faster, and we are getting better and better at simulating flow over airplanes with the computer. So the trend is definately to use the computer simulation more in design, and use the wind tunnel for final validation and to explore the things the computer can't do. At the same time, computers let us share information easier, so there is a whole new field of how to have designers collaborate better. Another thing that is changing is more competition from other airplane companies in other countries. To stay competitive, we will need to design airplanes that not only perform well, but are easier and faster to build, so our companies are more profitable. A big change in the future will come when we don't have enough fossil fuels left to power our whole civilization, but especially aircraft. There are not realy very good alternatives for powering airplanes. So there will be research on propulsion using alternate fuels, and also the related research of what the airplanes should be shaped like to work with those fuels. Example: Hydrogen fuel must be stored in a huge tank, so how can you shape the airplane to store the fuel it needs?

[ SteveSmith/ARC - 32 - 10:32:53 ]
RE: [Sarang] Sir,what are the opportuinties for a research are open for a an aerospace engineer?
Well, right now, not very many opportunities in aeronautics. Hopefully that will change soon. New types of materials for building airplanes, and new manufacturing methods to assemble them faster, and easier to maintain. Those are areas where people are doing a lot. Another area with a lot of opportunity is in the area of air traffic control.. We are working on better ways of managing the air traffic around airports and also criss-crossing the country going every which way, without running into each other. We need better tracking information, and then help from computers on how to organize the traffic flow. So those are some new areas.

[ SteveSmith/ARC - 33 - 10:39:11 ]
RE: [Sue] Hi Steve--The "encompassing wing" the kids are referring to are like on the B2 stealth bomber, where the wing is attached to the full length of the fuselage. How is this an advantage/disadvantage in terms of gliding characteristics?
Oh, I see, like a flying wing.....That type of airplane has two main advantages. First, if you can carry the payload in the wings, spread out sideways, the wing structure can be much lighter, because it doesn't have the bending stress from having all the weight in the middle, and all the lift in the wings. By putting more weight out in the wings, it cancels the bending moment from the lift. The other advantage is that it doesn't have the drag and weight from the fuselage. But the disadvantage is that without a horizontal tail to provide stability and control, the wing itself can not be designed to be as efficient. There are trade-offs on the wing shape to make it stable, and to make the wing controls work to control the airplane. I helped design a foot-launched sailplane like a hang glider, called the SWIFT. There is one on display at the aviation museum in San Carlos, CA. For gliders, it still works out that it is better to have a fuselage, mostly to provide a place to put the horizontal tail. The other thing about making a flying wing airplane, is if you want to put people in it, and have them sit in the wings, You find out how thick the wings have to be to make room for the passengers to stand up. So you end up designing a really HUGE airplane. It would be nice if people were smaller!

[ SteveSmith/ARC - 36 - 10:42:56 ]
RE: [njuguna] What would you say about the pricing of costs in Nasa research centres let say, AMES as compared to other centres in Europe like the DNW?
This is an iteresting question. In the past, NASA, as part of the government, has done work to help american companies, without charging much money. This was to help keep american companies more profitable, and more competitive in the world economy. But this is changing. We at NASA are now supposed to charge the real costs for what our research costs. This has 2 problems. One is we are not very good at figuring out how much it costs, because we didn't used to keep track. Also the companies are not used to having to pay so much - because they used to get the benefits of our research much cheaper. So now, the companies are trying to decide how much they can afford to spend on our research, and how much they can do by themselves. This is another reason why aeronautics research is not funded very well right now. I think the problem will work itself out.

[ Sandy/NASAChatHost - 37 - 10:44:34 ]
EVERYONE: We have about 20 minutes left in today's chat with Steve. When it's over please let us know how we've done by filling out the short chat survey at: http://quest.arc.nasa.gov/qchats/qchat-surveys

[ SteveSmith/ARC - 38 - 10:45:13 ]
RE: [Sue] Amy wants to know: Did the magazines and books you read as a kid influence your research and design interests?
WEll, I had several books on history of aviation. I used to study those a lot. I especially liked the fighter planes of world war II. I also read Aviation Week because my father brought it home from work. But when I was a kid, my main interest was birds. I wanted to be a biologist. It wasn't until high school that I found how much I like building and designing things, and How exciting it is for me to figure out how things work.

[ Sue - 39 - 10:47:50 ]
Wow! Thanks for the great response. Looks like we have our next design project!

[ SteveSmith/ARC - 42 - 10:48:37 ]
RE: [Sarang] what are the shapes of the wings of the aircrafts you design in order to get min. air resistance as well as speed?
Well, the wing shape really depends on what the purpose for the airplane is. Gliders have very long, slender wings, we call that "high aspect ratio" so that the drag that comes from making lift is very small. But those wings are too heavy for some airplanes, and not very maneuverable. A maneuverable airplane, like for airshows, or a fighter plane, has much shorter, stubby wings. The drag is higher, but they need the short wings for maneuverability, so thats what you call a design trade-off. Commercial jetliners are designed to fly about 85% of the speed of sound, and at this speed, the wings must have sweepback to keep the compressibility drag small. But they also have pretty high aspect ratio, so low drag from lift too.

[ Sue - 44 - 10:51:28 ]
We appreciate the time you took to be on-line with us today. This is our first on-line chat; it was exciting to be able to ask questions of a real expert! Your answers have been very helpful--thanks for encouraging this group of potential aeronautical engineers!

[ SteveSmith/ARC - 45 - 10:51:52 ]
RE: [Sue] Malorie wants to know: If you had unlimited funding, what project would you most want to research??
Wow, what a great question. I guess my favorite projects are trying to do better design optimization with the computer, so we need to get good flow simulations, and connect them with special procedures that change the design and see if it works better in the simulation.. There are lots of design constraints that come into the problem - like making sure it takes off on a certain length runway, and making sure it can fly safely if one engine stops, and making sure it can fly to the desired destination with some reserve fuel left over. We call this design synthesis. Thats my favorite.

[ Sandy/NASAChatHost - 46 - 10:52:24 ]
EVERYONE: THere are only 10 minutes left in the chat today... Don't forget to fill out our short survey when the chat is over: http://quest.arc.nasa.gov/qchats/qchat-surveys

[ Sandy/NASAChatHost - 47 - 10:53:20 ]
RE: [Sue] We appreciate the time you took to be on-line with us today. This is our first on-line chat; it was exciting to be able to ask questions of a real expert! Your answers have been very helpful--thanks for encouraging this group of potential aeronautical engineers!
Sue: You and your students asked some awesome questions! Thank you for participating today -- it's obvious you did your homework before coming to the chat! Hope you can join us again for another chat soon!

[ SteveSmith/ARC - 49 - 10:54:10 ]
RE: [njuguna] With a total of about nine JSF test flights accidents, would you attribute the failure with anything to do with the complicated aircraft desing involved and do you think this is something that can be sorted out by R&D, paticularly the windtunnel tests? Thanks!
Hmmm, I don't know much about these. I do know that it is a very complicated airplane, one of the biggest challenges is flying the airplane unstable. The natural design, and the center of gravity are made to make the airplane more maneuverable, but it is not stable by itself. A sophisticated computer controller has many sensors about the motion of the airplane, and provides artificial stability. If anything goes wrong with the computer or the sensors, it will probably crash.

[ Sandy/NASAChatHost - 51 - 10:55:36 ]
EVERYONE: Please don't send anymore questions and Steve will do his best to the answer the remaining few...

[ SteveSmith/ARC - 52 - 10:57:44 ]
RE: [njuguna] Steve, I am quite concerned about the funding of R&D, does this reflect the future of aviation? A few months ago, the Deputy President, Lockeed Martin mentioned that the Engineers that aviation is focusing on are IT specialists with interest in Aviation, what does this mean to you?
Well, right now, everyone is excited about information technology, but not really sure what the best thing to do with it. Our web chat is a good example - we couldn't do this a few years ago. Its a great idea to be able to communicate so easily. But, how do we translate that into doing engineering more easily? Better? its really hard to say....but thats what everyone is interested in right now. So, to combine them, we need engineers that understand the potential of what could be done, and then, when they get an idea, they can develop it and share it with the new IT. but its still not clear how that will figure into design....

[ SteveSmith/ARC - 53 - 11:00:11 ]
RE: [Sue] So, your last answer gave us another question: It seems that larger area on wings is good for gliders that need lots of lift, whereas smaller wings give more maneuverability. What size tail (in relation to the wing size) makes for the longest glide distance on a glider? Does the size matter much?
Yes, you want the horizontal tail to be big enough to do its job, but not any bigger, since it would be extra drag and weight. a good rule of thumb is 15 to 20 percent of wing area. Many newer gliders for radio control and hand launch are making smaller tails, but using a longer fuselage, so the tail effectiveness is still good, but with a very small tail. Of course, it is important to make the fuselage very light....they are using carbon fiber tubes that are made for kites.

[ Sandy/NASAChatHost - 54 - 11:00:52 ]
Ok Everyone, it's time to let Steve get back to work today! Thank you so much for participating today! You really asked some great questions! We hope you can come back and join us for another chat next week. Check out our chat schedule at: http://quest.arc.nasa.gov/common/events

[ SteveSmith/ARC - 55 - 11:05:16 ]
RE: [Sarang] Sir,what are the speeds of the fastest of aircrafts that are available on the earth?and what about the spacecrafts?
Well, the fastest airplanes go about Mach 3, or 3 times the speed of sound. it is possible to go about mach 5, but so far, there has not been a good reason to do that since it wastes a lot of fuel. Spacecraft go much faster. Without air resistance, you can go really fast. I think the space shuttle in orbit goes about 20,000 miles per hour. maybe a little less. But its really fast. It would be interesting to figure out how fast a geosynchonous satalite must go to stay in one spot over the earth.... But unfortunately, spacecraft speed is limited by how much fuel you can get up there, which takes bigger booster rockets. Maybe if we stored fuel in a tank up there with several trips, we could get enough fuel to go very fast, like half the speed of light or so - but even at that incredible speed, it would take a long time to reach the nearest star. So I don't know if we will do it anytime soon.

[ SteveSmith/ARC - 58 - 11:13:28 ]
RE: [Sarang] Sir, have you ever designed the hypersonic aircrafts?and are they built with some other technology than that of an ordinary aircraft?
Actually, yes, I've been helping on a hypersonic design for a reusable space plane. My part has been to make it fly well at low speeds too. This is hard because the requirements for hypersonic flight are so different, its hard to make the same shape fly slow. The space shuttle is actually a really smart design!

[ SteveSmith/ARC - 59 - 11:16:45 ]
RE: [Sarang] Sir,what are the possibilities in near future that our spacecrafts would explore our galaxy ,although a natural speed limit is given by time?
But unfortunately, spacecraft speed is limited by how much fuel you can get up there, which takes bigger booster rockets. Maybe if we stored fuel in a tank up there with several trips, we could get enough fuel to go very fast, like half the speed of light or so - but even at that incredible speed, it would take a long time to reach the nearest star. So I don't know if we will do it anytime soon.

[ SteveSmith/ARC - 61 - 11:20:43 ]
Thanks everyone for coming, and thanks to Sandy for organizing this!

 
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