Aero Team Online QuestChat

Date: October 15, 2001

Featuring: Dr. Sylvia Johnson
Ames Research Center

Mon Oct 15 http://quest.arc.nasa.gov/aero/events/centennial/

[ Lori/NASAChatHost - 1 - 12:35:36 ]

Welcome to the Centennial of Flight Webchat with Dr. Sylvia Johnson. Please read the expert's profile prior to the event.

[ Lori/NASAChatHost - 1 - 12:35:36 ]
You may go ahead and place questions in the chatroom now to be answered during the webchat. Please don't post test messages or repeats -- though you may not see your question, it is in the chatroom. Again, PLEASE do not repeat your questions. Enjoy the chat :-)

[ Lori/NASAChatHost - 4 - 08:37:54 ]
Good morning to our early arriving participants! If you haven't read Dr. Johnson's bio yet, you still have time. The webchat will begin in about 20 minutes or so :-)

[ Lori/NASAChatHost - 5 - 08:59:23 ]
Hello everyone! I would like to welcome you all to our first webchat of the day with Dr. Sylvia Johnson. Welcome Sylvia!

[ SylviaJohnson/ARC - 6 - 09:00:52 ]
Hi everyone! It is great to be here.

[ SylviaJohnson/ARC - 14 - 09:06:56 ]
RE: [Caitlin] 1. Why did you choose to become an engineer? 2. What are your goals?
First, engineering and science are fun! Seriously, I do like to know how and why things work, and to have an opportunity to do and make things work myself.

[ SylviaJohnson/ARC - 15 - 09:07:29 ]
RE: [Lyla] What exactly is a ceramic?
That is a good question. We can think of ceramics as being materials which are nonmetallic and inorganic. This makes them things like oxides (aluminum oxide or silicon dioxide (sans!)). There are also borides and carbides and nitrides and other materials.

[ SylviaJohnson/ARC - 17 - 09:10:26 ]
RE: [Rose] In general, how are thermal protection materials changing aerospace designs?
It is expensive to send things into space. We want to make sure that the thermal protection system keeps the spacecraft safe, but weighs as little as possible so that the payload can be bigger (this means more science or people or cargo). We have some new materials which we think will let us make vehicles which have sharper leading edges (see how blunt the shuttle is). With these designs we can have more maneuverable vehicles which are safer and more efficient

[ SylviaJohnson/ARC - 23 - 09:14:43 ]
RE: [Rose] What new technologies are emerging?
One of the newest technologies is in ultrahigh temperature ceramics. These are borides and carbides that can work at very high temperatures.

[ SylviaJohnson/ARC - 24 - 09:15:21 ]
RE: [Caitlin] Are there different types of ceramics? If so, are the degradation patterns different for each type of ceramic?
These new ceramics are not really new but are receiving more attention. They are very hard and very refractory (means that can withstand heat). They are also difficult to make.

[ SylviaJohnson/ARC - 31 - 09:18:39 ]
RE: [Jackie] I read your bio. What do you mean by "the mechanical behavior of ceramics"?
Mechanical behavior means how strong a material is.

[ SylviaJohnson/ARC - 32 - 09:18:58 ]
RE: [Doug] How can you tell if you materials will work in high speed reentry?
We test materials with "arc-jets". These are facilities here at Ames which simulate the pressures and temperatures and heat fluxes that are expected during reentry (to Earth and to planets such as Mars).

[ SylviaJohnson/ARC - 33 - 09:19:37 ]
RE: [Caitlin] Are there different types of ceramics? If so, are the degradation patterns different for each type of ceramic?
There are many different types of ceramics, and they all behave differently. For example, oxides already contain oxygen and do not degrade in an oxidizing environment. Nitrides or carbides however, will tend to oxidize, although this may not occur until high temperatures. Nitrides and carbides may be much more refractory and thus will not deform or creep as readily.

[ SylviaJohnson/ARC - 34 - 09:19:53 ]
RE: [Cyndi] What's your favorite part of your day?
I like all parts of the day! The morning is a challenge because I never know what will happen. I also do like going home to my family!

[ SylviaJohnson/ARC - 35 - 09:20:52 ]
RE: [Sean] How do you figure out how to make new ceramics?
We use our experience and what we know about existing materials and classes of materials. We also know how we want the microstructure to look, to get certain properties. To actually make them, we start with standard techniques and modify these as we go along -- we experiment!

[ SylviaJohnson/ARC - 40 - 09:22:38 ]
RE: [Randy] What is SHARP & why is it important?
By SHARP, what we really mean is the ability to make the leading edges (nose and the front of any wings etc) very sharp, that is, not blunt. What this means is that a vehicle can maneuver more easily, that is has a higher lift to drag ratio. This means that it can come back at more pints in the orbit, or can abort safely on liftoff if there is a problem. To make sharp leading edges we need high temperature materials because high speeds mean that the materials get very hot.

[ SylviaJohnson/ARC - 41 - 09:25:35 ]
RE: [Dave] How do these new technologies differ from the Shuttle Tiles?
Shuttle tiles are made from fibers such as silica and are very very porous, which makes them lightweight. These are great materials, and the space shuttles have been flying for 20 years. The new materials for sharp leading edges are ultrahigh temperature ceramics. These are not made from silica, and they are much more dense. They have a higher temperature capability. They are also made differently. Materials must always be matched to the application!

[ SylviaJohnson/ARC - 43 - 09:27:51 ]
RE: [Greg] What are borides and carbides?
Borides and Carbides are materials that contain boron or carbon atoms. For example, silicon carbide has the chemical formula SiC. An example of a boride is zirconium boride, which is ZrB2 (sub). Oh, and there is a material boron carbide, or B4C ( a very hard material used for armor applications).

[ SylviaJohnson/ARC - 46 - 09:30:13 ]
RE: [Sandy] Did you always like ceramics? Did you take a pottery class?
I first learned about ceramics in high school. I did not take a pottery class, although at the university we learned all the elements of traditional ceramics from a well-known artist. I have also made various pottery things in various summer jobs and at school. There is much to be learned in pottery -- glaze chemistry is very interesting, and you can make some beautiful colors.

[ SylviaJohnson/ARC - 48 - 09:32:10 ]
RE: [Sarah] do you ever feel that you are treated differently because you are a woman?
I was definitely treated differently because I was a woman when I was a student, and early in my career. I have always been determined to show that women and men have the same abilities. Things are a lot better nowadays, and I am delighted to see so much interest from young women in this chat room. Remember you can do anything you want!

[ SylviaJohnson/ARC - 52 - 09:35:30 ]
RE: [Tony] How can a new material make such a big difference in the design of a spacecraft/
Of course, there are many aspects that go into designing a spacecraft! There are thermal protection materials all over it, and the type depends on the conditions that that part will see. However, analysis of the performance of various shapes and configurations has shown how beneficial it would be to have very high temperature materials on the leading edge. It just so happens that the materials on which we are working seem to be very appropriate. There are other approaches as well -- coatings for example must also prove useful. In short, it is the capability of properties of the material which make the difference.

[ SylviaJohnson/ARC - 54 - 09:37:20 ]
RE: [Tom] What other things does NASA use these ceramic products for?
In my branch we use these materials primarily for thermal protection. However, TPS materials have been investigated for biological applications (bone growth templates). We are interested in other structural applications of the ceramics -- some engine parts might be a possibility.

[ SylviaJohnson/ARC - 57 - 09:39:23 ]
RE: [Leslie] Do you miss Austrailia? Do you ever go back & visit?
I do miss my mother and my brothers and my nieces and nephews! I also miss the beach, meat pies and the seafood. I like to go back when I have the time.

[ SylviaJohnson/ARC - 58 - 09:41:21 ]
RE: [Ginger] Why does the shuttle need tiles for reentry but not during launch & leaving the atmosphere?
The highest temperatures occur on reentry into the atmosphere and are caused by the flow of the gases over the vehicle. When the shuttle goes up it is leaving the atmosphere and can radiate heat into space. On reentry, the closer it comes to Earth, the more dense is the atmosphere and so the heating effect increases.

[ SylviaJohnson/ARC - 59 - 09:43:33 ]
RE: [Blaber] About what percentage of funding and manhours goes into researching ceramics and protecting the space shuttle?
I do not know the exact number for the space shuttle because much of the work to do with keeping it flying is done at Johnson and Kennedy Space Centers. We do work here on upgrading shuttle tiles -- making new coatings and improving materials. The budget varies from year to year. As for the UHTCs, we have enough funding now to make some progress, so I am happy.

[ SylviaJohnson/ARC - 62 - 09:45:08 ]
RE: [Blaber] What heat do they bake the tiles and what heat can they withstand?
They heat the tiles at around 1200C. The tiles are made primarily of silica. Silica melts at 1720C. The addition of other materials can make the tiles last at higher temperatures. Of course, the melting temperature is above the use temperature!

[ SylviaJohnson/ARC - 65 - 09:47:32 ]
RE: [Greg] How can you tell when a material fails at thermal protection?
We can tell during testing if it cracks, falls apart or a lot of the material is lost (recession). We also measure the temperature behind the tile to see how hot it gets. Tiles can fail during reentry, but this does not happen very often -- these materials perform very well. If a material fails, then it will allow the structure to heat up too much, which could cause it to fail.

[ Lori/NASAChatHost - 66 - 09:50:04 ]
Don't forget we have another chat with Imelda Terrazas-Salinas this afternoon. See our Calendar of Events for times, and for dates & times of other events scheduled this week and next for the Centennial of Flight Celebration. See: http://quest.arc.nasa.gov/projects/aero/centennial/ and http://quest.arc.nasa.gov/calendar/index.html.

[ SylviaJohnson/ARC - 67 - 09:50:45 ]
RE: [Caitlin] How do you join ceramics? What does the application of polymers do for the ceramics?
There are a number of colleges which have degrees in ceramic engineering or materials. I did ceramic engineering as an undergraduate, and then did graduate degrees in materials science with an emphasis on ceramics. You could go to the American Ceramic Society website to learn about colleges. There are some polymers which contain inorganic, as well as organic atoms. When they are heated up, the organics go away and the inorganics are left. For example, silica may be left. We can use these polymers to help us make coatings or to process (make) ceramics because they are often liquids and leave behind a ceramic material on heating.

[ SylviaJohnson/ARC - 68 - 09:52:12 ]
RE: [Leah] Have you ever seen a launch or the shuttle up close?
I saw a launch from the beach at Cocoa Beach -- the whole night sky lit up! I would love to see one close up! I have looked at the shuttles in the facility where they check them out before and after flight. They are very impressive.

[ Lori/NASAChatHost - 69 - 09:52:39 ]
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[ SylviaJohnson/ARC - 72 - 09:53:53 ]
RE: [Erik] How long have you been at NASA & how did you get to the job you have now?
I have only been working at NASA for about 18 months. Before that, I spent many years working for a research institute, doing ceramics. One day someone I know called me and told me about this job. They persuaded me to come and have a look , so I did and here I am!

[ SylviaJohnson/ARC - 74 - 09:57:16 ]
RE: [Elena] How do you compare schools in Australia to schools in America?
My son is now in high school here, and that seems very different to when I went to high school in Australia. I went to a girls school run by the state. Of course, we wore uniforms (including hats and gloves) and could not leave the school. We worked hard because we had statewide exams to pass to get into the university. My university experience there was fun. Graduate school in the US is excellent, and I am very glad that I had the opportunity to study here at Berkeley.

[ SylviaJohnson/ARC - 75 - 09:59:54 ]
RE: [Jesse] What is a normal day like for youz?
I get up early at 5:30 because I live a long way from work. My kids are old enough now to get themselves ready for school, and my husband gets them off. I drive a long way, but that gives me an opportunity to plan my day. At first I try to answer my e-mail and check my calendar. Then I get ready for meetings -- there are an awful lot!. I like to walk around the labs and see what people are doing and if I can help. I talk to my boss and let him know what is happening. At the end of the day, I am tired and it is a long drive home. I am always glad to see my family.

[ Lori/NASAChatHost - 76 - 10:01:26 ]
We have time for Sylvia to answer one more question! What great questions you all asked today!

[ SylviaJohnson/ARC - 77 - 10:01:42 ]
RE: [Colin] How many different types of thermal protection materials are there?
There are many different materials. However, we often think of them as reusable and ablators (or non-reusables). We can also divide the reusable materials up into rigid materials such as tiles, and flexible materials such as blankets (these are a bit like quilts, and make it easier to cover large areas).

[ SylviaJohnson/ARC - 78 - 10:05:06 ]
RE: [Blaber] I am a Independent study student. How could we incorperate material science into a class project?
I am glad you are interested in materials science! First many of the professional societies have local sections who have access to study guides. You can go to the Ceramic Society web site to check out educational activities. They can also direct you to local people. There are many experiments that are simple that you can do even without labs. There are also some basic books. There is one by van Vlack, updated by Shackelford which is for undergrads but has some good info (called Elements of Materials Science). You should also try other professional societies such as TMS, ASM, and the Materials Research Society. Good luck!

[ Lori/NASAChatHost - 79 - 10:05:19 ]
I want to thank you all for joining us today. A big thanks to Dr. Sylvia Johnson for sharing her time and NASA expertise with us today! Join us this afternoon for our next webchat. Have a great day all :-)

[ SylviaJohnson/ARC - 80 - 10:06:38 ]
I want to thank all of you for the great questions and interest you have in space and materials. Materials science is fun, and you can see how it applies to really interesting applications. Thanks and good bye.