Marshall Space Flight Center was the featured topic of last night's Live Chat. 66 were in attendance to hear Marshall's Scott Anderson talk about the history and mission of the center. Located in northern Alabama on the grounds of the Redstone Arsenal, Marshall is NASA's premier center for the development of rocket boosters. Launch vehicles for America's first satellite, first astronaut, and first man to the moon were all designed and tested at Marshall.
Marshall is also home to the research command center for the International Space Station. While launch control is at Kennedy and mission control is in Houston, this is where the science takes place (actually, it takes place in space, but here is where the results come). It also has the capability of acting as mission control should severe weather strike Houston.
Find out more by accessing the archive of the chat this weekend in the Live Chat archive off the Discover page, or on Monday in the INSPIRE Archive on the Home Page.
Friday, January 28, 2011
Wednesday, January 26, 2011
J-2X Progress: Valves, Commands into Action
By Bill Greene, MSFC, AL
Everyone seems to like analogies between the composition of a rocket engine and that of the human body. These are often colorful but not always helpful. In some cases, however, they work pretty well.
Okay, so let's start with your body as it is. Now, imagine removing all of your bones. Guess what? You're an immobile lump. Even if your brain is sending signals and your muscles are contracting, you're not really moving anywhere.
This time, let's instead start with your body as it is, but now imagine removing all of the muscles and tendons that connect the muscles to the bone. You've got a central nervous system and you've got bones, but with nothing to flex, the chain is broken and you’re stuck where you sit (assuming that you can still actually sit).
And, of course, if you instead start with your whole self and imagine removing your brain and/or your central nervous system that connects your brain to your muscles, again, you've achieved perfect immobility (i.e., you look like me on Saturday afternoons during college football season).
The point is that in order for you to be up and about, shoveling snow, doing laundry, playing pool, typing, whatever, you need both the command center that figures out what signals to send -- your brain -- and you need things that turn those signals into action -- your muscles and tendons and bones. In a rocket engine, the analogue for the brain is the engine controller. It is a computer that receives instructions from the vehicle and sends out commands to the engine pieces so as to fulfill those instructions. The analogue for the muscles are the valve actuation systems. These are the things that "flex" and cause movement. And the analogue for the bones, the final effectors that make things happen, are the valves.
The controller sends out signals and then the actuation system responds by shuttling pressurized working fluid -- helium for J-2X though some engines use hydraulic fluid instead -- where it needs to go so that the valves move and the engine comes to life. The engine goes from being a lump of inert, shiny metal to a "living" beast of flowing propellants, spinning turbomachinery, lots of fire, and thundering, rumbling thrust.
On the J-2X, there are 42 valves. Most of this number is made up of small valves like check valves, solenoid valves, and valves in small lines like the bleed lines. There are also a handful of big valves -- the primary valves -- that directly control the flow of propellant and, in one case, combustion products along the plumbing of the engine. Each of these primary valves is connected to a valve actuator, i.e., the muscle. These valve actuators convert the energy of high pressure helium gas into mechanical rotation of the valve. This is accomplished by pressurizing cavities and moving pistons and, in this way, the valve is pushed opened or closed. I've used this schematic shown below before, but it is useful here as well since it illustrates the primary J-2X valves: Main Fuel Valve (MFV), Main Oxidizer Valve (MOV), Gas Generator Fuel Valve (GGFV), Gas Generator Oxidizer Valve (GGOV), and the Oxidizer Turbine Bypass Valve (OTBV).
The control logic for J-2X is relatively simple. The whole subject of different kinds of control logic is a good topic for a future article, but suffice it to say that for normal operation the J-2X: starts on command, can change between two power levels on command, and shuts down on command. The control system is designed to do other things as well, including monitoring the health of the engine, but these operations are the commanded functions. Start and shutdown can be simplistically thought of as: the valves open and the valves close. It’s a bit more complicated since the timing of opening and closing is extremely important, but the open/close notion is basically true. The oddball action is the one consisting of changing power levels. That is accomplished by controlling the power to the oxidizer turbine via the OTBV. This bypass valve effectively allows for limited, independent control of the two turbopumps. By altering the power to the oxidizer turbopump (OTP), you can control the engine thrust level (and, simultaneously, mixture ratio).
The OTBV for J-2X is designed and built by Pratt & Whitney Rocketdyne (PWR), the prime contractor for the whole engine. In addition to being responsible for the “oddball action” on the engine of changing power levels, it represents a challenging design due to the range of operating conditions. Unlike the other primary valves on the engine that see, essentially, one narrow range of environmental conditions, the OTBV has to function in temperatures approaching 420 degrees below zero Fahrenheit (liquid hydrogen conditions) immediately prior to start and then, suddenly, within 1 second of ignition of the gas generator, see temperatures approaching 750 degrees above zero Fahrenheit (combustion products). That broad range of operating conditions requires special design considerations and special materials. Not only do you have to worry about wear and tear under such harsh conditions, but you also have to think about simple operation under the extremes of thermal expansion.
The original, Apollo-era J-2 engine also had an OTBV, but it was used slightly differently and was designed much differently. It was a butterfly valve whereas the J-2X OTBV is a ball valve.
No, the valves shown in the picture are NOT rocket engine valves. I can't show any internal workings of rocket engine valves. In fact, I am not even allowed to describe the general design details that make the J-2X OTBV kind of unique. However, the basic elements of rocket engine valve functionality for butterfly and ball valves are essentially the same as these water valves. The biggest difference is the replacement of the handles with pneumatically driven actuators. Back during the Apollo era it would seem that butterfly valves were most frequently used, but after many years of usage on the Space Shuttle Main Engine, ball valves are often preferred these days. They generally require less torque to move and they generate better flow characteristics and flow rate control capability.
The first OTBV unit for use on the upcoming development engine testing for J-2X is in the later phases of manufacturing at the PWR in Los Angeles. All of the individual piece parts are schedule to be complete by the beginning of February and assembly will begin the middle of February. The valve then will be integrated the actuator and shipped to the NASA Stennis Space Center to be put on the first engine.
Everyone seems to like analogies between the composition of a rocket engine and that of the human body. These are often colorful but not always helpful. In some cases, however, they work pretty well.
Okay, so let's start with your body as it is. Now, imagine removing all of your bones. Guess what? You're an immobile lump. Even if your brain is sending signals and your muscles are contracting, you're not really moving anywhere.
This time, let's instead start with your body as it is, but now imagine removing all of the muscles and tendons that connect the muscles to the bone. You've got a central nervous system and you've got bones, but with nothing to flex, the chain is broken and you’re stuck where you sit (assuming that you can still actually sit).
And, of course, if you instead start with your whole self and imagine removing your brain and/or your central nervous system that connects your brain to your muscles, again, you've achieved perfect immobility (i.e., you look like me on Saturday afternoons during college football season).
The point is that in order for you to be up and about, shoveling snow, doing laundry, playing pool, typing, whatever, you need both the command center that figures out what signals to send -- your brain -- and you need things that turn those signals into action -- your muscles and tendons and bones. In a rocket engine, the analogue for the brain is the engine controller. It is a computer that receives instructions from the vehicle and sends out commands to the engine pieces so as to fulfill those instructions. The analogue for the muscles are the valve actuation systems. These are the things that "flex" and cause movement. And the analogue for the bones, the final effectors that make things happen, are the valves.
The controller sends out signals and then the actuation system responds by shuttling pressurized working fluid -- helium for J-2X though some engines use hydraulic fluid instead -- where it needs to go so that the valves move and the engine comes to life. The engine goes from being a lump of inert, shiny metal to a "living" beast of flowing propellants, spinning turbomachinery, lots of fire, and thundering, rumbling thrust.
On the J-2X, there are 42 valves. Most of this number is made up of small valves like check valves, solenoid valves, and valves in small lines like the bleed lines. There are also a handful of big valves -- the primary valves -- that directly control the flow of propellant and, in one case, combustion products along the plumbing of the engine. Each of these primary valves is connected to a valve actuator, i.e., the muscle. These valve actuators convert the energy of high pressure helium gas into mechanical rotation of the valve. This is accomplished by pressurizing cavities and moving pistons and, in this way, the valve is pushed opened or closed. I've used this schematic shown below before, but it is useful here as well since it illustrates the primary J-2X valves: Main Fuel Valve (MFV), Main Oxidizer Valve (MOV), Gas Generator Fuel Valve (GGFV), Gas Generator Oxidizer Valve (GGOV), and the Oxidizer Turbine Bypass Valve (OTBV).
The control logic for J-2X is relatively simple. The whole subject of different kinds of control logic is a good topic for a future article, but suffice it to say that for normal operation the J-2X: starts on command, can change between two power levels on command, and shuts down on command. The control system is designed to do other things as well, including monitoring the health of the engine, but these operations are the commanded functions. Start and shutdown can be simplistically thought of as: the valves open and the valves close. It’s a bit more complicated since the timing of opening and closing is extremely important, but the open/close notion is basically true. The oddball action is the one consisting of changing power levels. That is accomplished by controlling the power to the oxidizer turbine via the OTBV. This bypass valve effectively allows for limited, independent control of the two turbopumps. By altering the power to the oxidizer turbopump (OTP), you can control the engine thrust level (and, simultaneously, mixture ratio).
The OTBV for J-2X is designed and built by Pratt & Whitney Rocketdyne (PWR), the prime contractor for the whole engine. In addition to being responsible for the “oddball action” on the engine of changing power levels, it represents a challenging design due to the range of operating conditions. Unlike the other primary valves on the engine that see, essentially, one narrow range of environmental conditions, the OTBV has to function in temperatures approaching 420 degrees below zero Fahrenheit (liquid hydrogen conditions) immediately prior to start and then, suddenly, within 1 second of ignition of the gas generator, see temperatures approaching 750 degrees above zero Fahrenheit (combustion products). That broad range of operating conditions requires special design considerations and special materials. Not only do you have to worry about wear and tear under such harsh conditions, but you also have to think about simple operation under the extremes of thermal expansion.
The original, Apollo-era J-2 engine also had an OTBV, but it was used slightly differently and was designed much differently. It was a butterfly valve whereas the J-2X OTBV is a ball valve.
No, the valves shown in the picture are NOT rocket engine valves. I can't show any internal workings of rocket engine valves. In fact, I am not even allowed to describe the general design details that make the J-2X OTBV kind of unique. However, the basic elements of rocket engine valve functionality for butterfly and ball valves are essentially the same as these water valves. The biggest difference is the replacement of the handles with pneumatically driven actuators. Back during the Apollo era it would seem that butterfly valves were most frequently used, but after many years of usage on the Space Shuttle Main Engine, ball valves are often preferred these days. They generally require less torque to move and they generate better flow characteristics and flow rate control capability.
The first OTBV unit for use on the upcoming development engine testing for J-2X is in the later phases of manufacturing at the PWR in Los Angeles. All of the individual piece parts are schedule to be complete by the beginning of February and assembly will begin the middle of February. The valve then will be integrated the actuator and shipped to the NASA Stennis Space Center to be put on the first engine.
Tuesday, January 25, 2011
Poll of the Week: Fly Me to the Moon?
Here are some selected comments from the Discussion Board:
I, personally, would wait until I get the feedback of those who have gone there already.
Then, I would be sure about problems and what not, how comfortable it is, and the daily routine.
This would also ensure that I will come back alive!
Yes. Absolutely, positively, definitely, 100.00% yes. When do we leave?
I love the moon! I'll gladly time travel back to the Apollo era and hop aboard the Saturn V! I would like to come home after a while, but a vacation on the moon doesn't sound like a bad idea.
Again, I want to be the guy on Earth controlling that thing/building the rockets. I might go as a short vacation, but...
Well, I would definately go in a heartbeat. But, I would want to come back down to Earth after a while. So, a vacation sounds good.
I'd go there in a heartbeat too! I would be willing to live there as long as I could periodically visit our family, friends, and Earth. It would be so cool to be in a lunar colony!
LOL sure. After all, someone has to build and plan it, or it never gets off the ground.
Just be sure the problem solving guide/instruction manual thing whatever it's called has "Don't Panic" on the cover...
Thanks for participating in our polls, and look for the new poll to be posted Tuesday afternoon!
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| "Orbit Buddy" by =Royaba |
Friday, January 21, 2011
Live Chat Roundup: January 20, 2011
Did you know there is water on the Moon? Did you know there was a LOT of water on the Moon? That discovery and how it was made was presented by Tony Colaprete from the Ames Research Center. Tony is the Principal Investigator for the LCROSS (Lunar Crater Observation and Sensing Satellite) mission and previewed a presentation he will give later this month to a science conference in Israel. 63 members of the INSPIRE Online Learning Community were in attendance for the presentation and the Q&A that followed.
LCROSS piggybacked its mission with the LRO (Lunar Reconnaissance Orbiter), being composed of a modified adapter ring and spent Centaur second stage. LCROSS itself trailed the Centaur, allowing it to impact first into the lunar surface and taking observations which were immediately relayed to Earth. The LRO and Earth based telescopes also imaged the impact. The goal of the impact was to blast surface material into space and make spectrographs of the ejecta. While visually disappointing, a wealth of information was recovered by LCROSS. Tony Colaprete and his team have poured over the data during the year following the impact, and are now releasing their findings: the Moon is wet. This conclusion is verified by other orbiting spacecraft from other countries.
The benefits of finding this lunar water are many. Historically, it helps piece together the Moon's past, giving more information about the creation of the Solar System. Lunar water also offers an in-situ supply for future expeditions. This water can then be broken down to oxygen (needed for life support) and hydrogen (fuel).
If you missed the chat, you can find it in the archives in the Live Chat section off the Connect page, or on Monday in the INSPIRE Archives on the Home Page. DOn't forget to copy the pass code and take the quiz!
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| Visual spectrum image of the LCROSS impact |
The benefits of finding this lunar water are many. Historically, it helps piece together the Moon's past, giving more information about the creation of the Solar System. Lunar water also offers an in-situ supply for future expeditions. This water can then be broken down to oxygen (needed for life support) and hydrogen (fuel).
If you missed the chat, you can find it in the archives in the Live Chat section off the Connect page, or on Monday in the INSPIRE Archives on the Home Page. DOn't forget to copy the pass code and take the quiz!
Wednesday, January 19, 2011
NASA's First Android App
By Jason Townsend
You've probably heard all the hype about Tang being invented as a drink for the astronauts. Well, we hate to say this -- but that's not true. But lots of other amazing technologies have been invented by NASA or through NASA-funded research and now we've got an App for that.
The NASA Spinoff App highlights the direct impact NASA innovations have made on the everyday lives of citizens. Commercialization of NASA technology has contributed to products and services in the fields of health and medicine, transportation, public safety, consumer goods, environmental resources and computer technology.
This is NASA's first Android app and allows you to explore NASA technologies developed in your own backyard. The App contains a feed of NASA’s latest technology news, a searchable database of NASA-derived innovations, a map of spinoff locations, a historical timeline and a database of NASA’s available licensing opportunities to inspire the spinoffs of the future.
Additional Android, iPhone, iPad and other Apps are in the works. We'll continue to keep our list of Apps fully up to date. But in the meantime, explore our newest NASA App and learn about how space technologies are impacting life right here on Earth.
Wednesday, January 12, 2011
Where are the archives?
By INSPIRE Staff
Some of you may want to beef up your point totals for your Summer STEM Experience application by checking out old Live Chats and taking the quizzes associated with them. You’ve come here to the Connect page, clicked the Live Chat link on the left and then selected Archives to find ... nothing! Well, don’t worry; they are still available. The Archives here are bridged directly from the Elluminate website, and yesterday the bridge went down. When we restored it, the links to the archived chats were lost. But, as I said, there is another way!
Navigate back to the Home page and look at the bottom of the left hand column for the “Live Chat Archive” link. There, you will find every chat sorted by month, and even have the option to open up the Elluminate file itself, or download an audio (MP3) or video (Quicktime) version of the chat. Any one will provide you with all the information you need to enjoy the chat and then access the quiz (the password for the quiz will be found at the end of the chat). While the Archive off the Connect page has been a convenience, the official INSPIRE Archive has always been found on the Home Page.
As always, if you have any questions about this, contact INSPIRE support at nasainspire@okstate.edu.
Tuesday, January 11, 2011
Poll of the Week: Favorite Part of the OLC?
This weeks poll asked your opinion on the OLC:
Over half of you chose the Home Page as your favorite part of the OLC. Second was the Discussion Board, followed by the Leaderboard. This blog and the Showcase rounded out the remaining votes. Thanks to all who left their vote!
Though the Discussion Board came in second, it was busy as many posted opinions on their votes. Here are some selected posts:
“My favorite part of the OLC are the fun activities and talking to kids my age who know about science!”
“I also think the Discussion board is the best place in the OLC. I enjoy the activities as well, but the OLC offer us the opportunity to share our knowledge and opinions directly. I have gotten to meet so many interesting people here and I think this is what makes us a group. The discussion board is our way to communicate and contact each other. “
“I think the home page is the best part of the OLC. It not only keeps you aware of activities, chats, and news in the OLC but also talks about what is going on in NASA and space, such as the lunar eclipse, the space shuttle launch, and space weather.”
“I like the Discussion Board because I think it's fun to discuss STEM news and subjects. Many of the discussions we have on here are about subjects featured on the home page, the blog, activities, and chats, so it encompasses a large part of the OLC. It's also fun to see other people's projects, like the Your Spin on Technology projects that are posted on the Discussion Board. It connects the OLC, so it's my favorite part.”
“I believe the best part of the OLC is definitely the leader board. I'm a competitive person, and now that ... I finally have time to get more involved, I'm going to enjoy climbing up those ranks. They add an incentive to work harder, show you where you are in relation to your OLC peers, and are nicely incoporated into a bulletin board design nonetheless. I really like the way the entire site is designed, but the leaderboard adds an extra layer of challenge for me.The home page comes in for a close second, followed probably by the discussion board. The Showcase has some pretty neat programming design behind it (the Summer Experiences category's picture expansion is well-concieved), but it doesn't have much meat to it yet.”
“Have to agree with you here. The home page changes at least once a week, and I love seeing all the recent news in the science world. I don't think I'd ever hear about some of these things without it. The weekly polls are really neat too because they let us see what other people like us think about some interesting topics. I have to say though... there are some really great activities when I have the rare time to do them.”
Thanks for all your opinions! And if you have not taken the poll and left your mark on the Discussion Board, why not join in the fun? Each week, you’ll find a new Poll available on Tuesday afternoon. Have an idea for a Poll? Check for the special “Poll Ideas” dropbox (they’re linked from the Connect page) and drop in your idea.
J-2X Progress: The Main Combustion Chamber -- the Heart of the Fire
By WIlliam Cooke, MSFC, AL
My background is analytical modeling. There are all kinds of modeling in use today, including some extraordinary computational fluid dynamics and structural dynamics work that is amazing, but back when I did more hands on work I did zero/one-dimensional, system-level modeling of fluid systems, thermodynamics, and heat transfer. Rather than looking at the micro-level, my work was usually a step back at the macro-level.
I’ve told you all that because, over the years I found that one of things that I found most challenging and most enjoyable to model is combustion devices. Take the main combustion chamber (MCC) as the prime example. Its job is to contain the combustion, squeeze the combustion products to sonic velocity, and then direct them towards the nozzle. It’s just a big, hourglass-shaped tube. It all sounds simple until you realize that those combustion products are at about 6,000 degrees Fahrenheit and, for the J-2X, at a pressure of over 1,300 pounds per square inch. How it is that the MCC doesn’t melt or burst – or both – is amazing.
So, let me tell you a little about MCCs.
The only way to build one where the walls don’t melt during operation of a large liquid hydrogen / liquid oxygen engine is to actively cool them. This means flowing cold hydrogen inside the walls. On one side of the wall you have combustion 6,000 degrees and on the other side, you have hydrogen that is typically entering at less than 100 degrees above absolute zero. Now you see why this is a delight for someone who enjoys modeling thermodynamics, fluid flow, and heat transfer.
How do you make walls that allow for active cooling? Well, years ago, back during the era of the Apollo Program the walls were made of tubes. They took a whole bunch of tubes, bent them into the profile shape of an MCC, stacked them up into a circular pattern, lay in or pack in binder metal, and then brazed them together. Brazing is essentially a welding process where you stick the whole thing into an oven, make it really hot, and the thing melts together (as someone who enjoys cooking, I tend to think of it kind of like a stiff metal stew). In this case what melts together is binder metal stuck between the tubes so that when you take it out of the oven, you've turned several hundred tubes into a single piece. Note that the regeneratively-cooled portion of the J-2X nozzle is made in this manner using tubes, but when doing this with an MCC where the pressures are higher and the temperatures are hotter: we've advanced a long way since the 1960's.
First of all, in order to make the tube-wall MCC structurally sound, you were kind of forced to use steel tubes (steel of some sort at least). What you'd really like to use is something like a copper alloy that has higher thermal conductivity properties. Copper tubes might be possible, but you would have to put behind them a steel support structure, a jacket of some sort. That, however, introduces potential issues of hot stuff or high-pressure stuff seeping behind the tubes and causing all kinds of problems including catastrophic failure of the engine. The hourglass geometry required for the combustion products flow path complicates nearly all of the structural issues.
Then, along came the development effort for the Space Shuttle Main Engine (SSME). Here you’re dealing with MCC pressures over 3,000 pounds per square inch so you needed a whole new approach since tubes just weren’t going to cut it. What they came up with, conceptually, is the same thing used by J-2X and most other large rocket engines, although the means for fabrication vary. They used a liner and jacket concept. The liner replaced the hundreds of tubes. It is a single piece with the hourglass shape within which the combustion takes place. Around the liner is fitted a structural jacket. Thus, the liner can be made of something like a copper alloy to deal with the heat transfer issues and the liner can be made of some steel or nickel alloy to deal with the structural issues. Where before the tubes provided the coolant flow path, here groove are cut into the backside of the liner so that when the liner and the jacket are fit together, these grooves become channels. Ta-da!
The first step in manufacturing an MCC involves hot spin-forming a copper-alloy forging. The resulting piece is then machined to a precise contour. The liner is then slotted, meaning that the grooves for the coolant flow passages are cut into the backside away from where the combustion products will flow past.
The really tricky part about this kind of MCC is making the whole thing fit together and stay together given the different metals being used. The different metals have different properties and different structures at the micro level so a variety of methods including electro-plating and brazing and welding methods are used to make a single unit. It is these details that are proprietary and export-controlled technologies that cannot be revealed but that make the whole thing possible. Luckily, this humble analyst knows little about metallurgy so there is almost no danger of me exposing something useful-but-sensitive to the world at large. In the past, developments for methods of producing a robust bond between the liner and the structural jacket resulted in cheaper, more reliable, yet heavier design. The J-2X design, however, has allowed for significant weight decreases by optimizing the design for post-bond machining.
Another recent innovation in MCC fabrication, and one being pursued for the J-2X MCC design, is the use of castings for the manifolds that distribute the coolant to the flow passages and collects the coolant at the end of the passages. These pieces of hardware see very high fluid pressures due to their function as manifolds but also are used by a number of other components for structural mounting into the engine system. Thus, they are heavy and complex pieces. In the past, the typical practice was to machine these parts out of wrought forgings. The J-2X cast manifolds offer a significantly more cost efficient way to produce these parts.
The MCC for the first J-2X development engine is currently planned to complete fabrication in early February 2011. All of the major parts for the second MCC are already in work including the manifolds, the liner, and the jacket. It is slated for completion in July. So now, analytical modelers, like me, will just have to sit back and wait for the testing to commence in a couple of months. Then the process of reconciling models to test results, understanding the clash of approximations and standard correlations and actual, particular physics, starts in earnest. That’s the truly fun part!
My background is analytical modeling. There are all kinds of modeling in use today, including some extraordinary computational fluid dynamics and structural dynamics work that is amazing, but back when I did more hands on work I did zero/one-dimensional, system-level modeling of fluid systems, thermodynamics, and heat transfer. Rather than looking at the micro-level, my work was usually a step back at the macro-level.
I’ve told you all that because, over the years I found that one of things that I found most challenging and most enjoyable to model is combustion devices. Take the main combustion chamber (MCC) as the prime example. Its job is to contain the combustion, squeeze the combustion products to sonic velocity, and then direct them towards the nozzle. It’s just a big, hourglass-shaped tube. It all sounds simple until you realize that those combustion products are at about 6,000 degrees Fahrenheit and, for the J-2X, at a pressure of over 1,300 pounds per square inch. How it is that the MCC doesn’t melt or burst – or both – is amazing.
So, let me tell you a little about MCCs.
The only way to build one where the walls don’t melt during operation of a large liquid hydrogen / liquid oxygen engine is to actively cool them. This means flowing cold hydrogen inside the walls. On one side of the wall you have combustion 6,000 degrees and on the other side, you have hydrogen that is typically entering at less than 100 degrees above absolute zero. Now you see why this is a delight for someone who enjoys modeling thermodynamics, fluid flow, and heat transfer.
First of all, in order to make the tube-wall MCC structurally sound, you were kind of forced to use steel tubes (steel of some sort at least). What you'd really like to use is something like a copper alloy that has higher thermal conductivity properties. Copper tubes might be possible, but you would have to put behind them a steel support structure, a jacket of some sort. That, however, introduces potential issues of hot stuff or high-pressure stuff seeping behind the tubes and causing all kinds of problems including catastrophic failure of the engine. The hourglass geometry required for the combustion products flow path complicates nearly all of the structural issues.
Then, along came the development effort for the Space Shuttle Main Engine (SSME). Here you’re dealing with MCC pressures over 3,000 pounds per square inch so you needed a whole new approach since tubes just weren’t going to cut it. What they came up with, conceptually, is the same thing used by J-2X and most other large rocket engines, although the means for fabrication vary. They used a liner and jacket concept. The liner replaced the hundreds of tubes. It is a single piece with the hourglass shape within which the combustion takes place. Around the liner is fitted a structural jacket. Thus, the liner can be made of something like a copper alloy to deal with the heat transfer issues and the liner can be made of some steel or nickel alloy to deal with the structural issues. Where before the tubes provided the coolant flow path, here groove are cut into the backside of the liner so that when the liner and the jacket are fit together, these grooves become channels. Ta-da!
The first step in manufacturing an MCC involves hot spin-forming a copper-alloy forging. The resulting piece is then machined to a precise contour. The liner is then slotted, meaning that the grooves for the coolant flow passages are cut into the backside away from where the combustion products will flow past.
Friday, January 7, 2011
Live Chat Roundup: January 6, 2011
Happy New Year!
Well, it is still the same school year, but when the digit changes it always marks the time for new resolutions. I have two: 1) Always live in the future - keep moving forward. And 2) When faced with a problem make the wisest choice possible. Feel free to share yours on the Discussion Board.
Now, on to last night's chat! We had 69 in attendance to hear Glenn Research Center's Roger Storm share about the history and work of the Center. Many students were surprised to learn at one time Glenn had a working nuclear reactor and today specializes in microgravity research. We also learned of Roger's TV game show experience! You can find out more by visiting the archive and viewing the Live Chat 1/6 Glenn Research Center. Don't forget to take the quiz to earn 50 points!
Next week, we will be hosting chats to help answer questions about the Summer STEM Experience applications. To give the most students the best opportunity to attend, we will host 6 chats. You will need to sign up on the Discussion Board for the chat you wish to attend. The dates and times are:
Our next Live Chat will be Thursday January 20 at 8:00pm CT. It will be on the results of the Lunar Reconnaissance Orbiter and will feature Anthony Colaprete of Ames Research Center, CA. Information on signing up for the chat will appear in the eINSPIRE communication on January 17th. See you then!
Well, it is still the same school year, but when the digit changes it always marks the time for new resolutions. I have two: 1) Always live in the future - keep moving forward. And 2) When faced with a problem make the wisest choice possible. Feel free to share yours on the Discussion Board.
Now, on to last night's chat! We had 69 in attendance to hear Glenn Research Center's Roger Storm share about the history and work of the Center. Many students were surprised to learn at one time Glenn had a working nuclear reactor and today specializes in microgravity research. We also learned of Roger's TV game show experience! You can find out more by visiting the archive and viewing the Live Chat 1/6 Glenn Research Center. Don't forget to take the quiz to earn 50 points!
Next week, we will be hosting chats to help answer questions about the Summer STEM Experience applications. To give the most students the best opportunity to attend, we will host 6 chats. You will need to sign up on the Discussion Board for the chat you wish to attend. The dates and times are:
- Monday, January 10 – 7:00pm CT and 8:00pm CT
- Tuesday, January 11 – 8:00pm CT and 9:00pm CT
- Thursday, January 13 – 7:00pm CT and 8:00pm CT
Our next Live Chat will be Thursday January 20 at 8:00pm CT. It will be on the results of the Lunar Reconnaissance Orbiter and will feature Anthony Colaprete of Ames Research Center, CA. Information on signing up for the chat will appear in the eINSPIRE communication on January 17th. See you then!
Monday, January 3, 2011
Poll of the Week: NASA's Christmas Wish
This weeks' poll was close, but the most popular NASA wish for Christmas was a larger budget! Here are some comments from the Discussion Boards:
Definately the budget. All the rest can be done with the budget.No, not a trick question, but it is sometimes these hard decisions that an administrator may face. Do you cut research where you may go years without a breakthrough, or operations that might decrease safety. It is not just how much money you get but also how you spend it. I hope you all enjoyed this little diversion, and can better appreciate the job that Mr. Bolden does for us!
I agree. It's a bit late for more shuttles, and with more funding NASA can continue its search for new life and clean energy.
I don't think we should consider the shuttles old stuff. New and improved shuttles would be great so we could have a U.S. spacecraft out there, but the concept of a reusable shuttle isn't a bad one. It can and should still serve us well.
Discovering life on another planet would spur astronomical interest and end up giving NASA a bigger budget.
I think that NASA should wish for a clean energy breakthrough. Although more money would mean that more things could be done, that doesn't mean that any of them would be succesfull. On the other hand, a clean energy breakthrough would be a concrete advancement that NASA could point to during budget negotiations with Congress to have a larger budget anyways. Additionally there will be all of the environmental benefits.
I'm starting to think this is a trick question...
This week asks a more local question: What is your favorite part of the OLC? Answer the Poll now on the Home Page, and then support your answer on the boards!
Astronomy Club
By Andrea Boria, INSPIRE 11th Grade
My passion and interest in astrophysics, aerospace engineering and the opportunities that NASA INSPIRE has brought me I decided to create an Astronomy club in my school. With the permission of the principal, professors and counselors in my school the dream of creating an organization of students who are interested in planetary sciences became true. My intention creating this organization is to educate and motivate students who are interested in science, technology, mathematics and engineering, the teaches in my school have been helping me with the education and field trips such as the Arecibo Observatory, between others. NASA have motivated me to invent this organization, being part of NASA team is my dream and I would like to motivate people to feel the same, to have goals in your life and love what you are going to do in a future.
Mission: The principal mission in the Astronomy Club is to increase interest and knowledge in planetary sciences, planetary systems, investigation of the Solar System, cosmology, between others.
Vision: Expand the horizons and knowledge in students about future careers. Promote NASA OLC and the opportunities that NASA have for high school students. Motivate students to study in STEM careers.
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