LiveChat Roundup: Sept. 29, 2011

How many math enthusiasts do we have on the OLC?  Raise your hands!  Yes, I thought quite a few!  You would have enjoyed joining the 167 participants in last night's LiveChat with Mr. David Seal of the Jet Propulsion laboratory in Pasadena, California.  Mr. Seal is a project manager who has worked on sending probes to Mars and planning the mission for the Cassini probe to Saturn.  He brought our INSPIRE students up to speed on what it takes to plot the trajectory to accomplish all the science to be done.

Read more about this image at http://apod.nasa.gov/apod/ap090111.html

It takes several years to plan a mission, and believe it or not, some of that planning is held off until a successful launch has taken place!  There is no sense to going through the expense of planning only to have you spacecraft fail to launch.  And often time a probe will be granted extra mission time and new goals are set with ways to reach them.  Part math, part science, part management, mission planning requires a host of skills!

Now, it is not too late to get in on the fun of our LiveChat!  All charts get archived and there are many ways you can have access to them.  The first is to follow the link on the right to the LiveChat room list.  In the upper left column will be a link to the Archive.  You may find the chat available later that night, but most certainly on Friday morning when the Roundup is posted.  The archive hosts the raw Collaborate Java file that opens up just like the live event.  You can use a slider at the bottom to fast forward if needed.  On Monday morning this same file will be posted on the Home Page Archive section where it is easier to find later in the year.  The Home Page Archive also hosts two other formats, a Quicktime .MOV and an MP3 version perfect for downloading to your smartphone or MP3 player.  Several students have said they download these and watch or listen on the ride to and from school.  And don't forget to stick around to the very end to find the password needed to unlock the quiz so you can collect 25 points!  If you want to chat about the LiveChat event, or have any questions for the speaker, go to the Discussion Board forum titled LiveChats and look for the appropriate thread.

One more item before we go: We have had questions from students who had problems getting on the LiveChat, so we created a video tutorial to explain the procedure.  You'll find it by clicking the Help link on the right column of the Home Page, then the Tutorials tab, then the link to Video Tutorials.  Sign up is open now for next week's chat on scientifically studying the weather, so put your name in now!

Plunging Over Niagara Falls In A Burning Barrel. And More.

By Astronaut Ron Garan, ISS Expedition 28

About two weeks before my return to Earth, I had a videoconference from the International Space Station with astronaut Scott Kelly who told me about his experience plunging over Niagara Falls in a burning barrel six months before. He was actually describing what his own ride home from the ISS on a Soyuz spacecraft was like. Now that I’ve taken the same trip, I can tell you that it was as advertised, and more.

Travel Day

I spent undocking day completing a biological study and stowing it onboard the Soyuz for return to Earth, packing cargo, taking some last minute pictures of our beautiful planet from the space station Cupola, and Tweeting pictures I took on my last full day in space. Following a brief goodbye to Mike Fossum, Satoshi Furukawa and Sergei Volkov, who remain onboard the space station, Sasha, Andrey and I hurried into our Soyuz spacecraft, closed the hatch and started preparing for undocking.

Once the hatch was closed, I put on special garments worn under my spacesuit to help counteract the negative effects of the g-forces we would encounter upon re-entry into Earth’s atmosphere. Sasha and Andrey also dressed in their spacesuits, and then we all strapped into the same seats we occupied when we launched from the Baikonur Cosmodrome in Kazakhstan on April 5, 2011. Andrey was on the left, Sasha in the middle, and I sat on the right.

Undocking

As the hooks securing our spacecraft released, springs pushed us slowly away from the space station. As we backed away, I took in my last views of the amazing orbital complex that we called home for five and a half months. I strained for a last glimpse of the outboard edge of the space station’s massive solar arrays through the window next to my seat.

We made a lap and a half around the Earth before the spacecraft fishtailed to point backwards, just as the moon was setting west of South America. Then, moments before passing the southern tip of the continent, I watched an orbital sunrise one last time. We then fired the main engines for about four and a half minutes, enough to slow us down for re-entry into Earth’s atmosphere.

The next big event during our return to Earth was the separation of our Soyuz spacecraft into three separate parts: the orbital compartment, the propulsion compartment and the descent capsule, the only part that would survive the transition through the atmosphere. Separation occurred with a small explosion followed by debris flying everywhere out my window!

G-forces Build

G-forces started to build soon after separation. I could see the atmosphere change to pink outside my window. North Africa and Saudi Arabia flew by as we approached Earth at a steep angle, at just under 5 miles per second. Fountains of sparks flashed as the g-forces built to 4.5 times normal gravity. Then flames, as the window burned black and opaque. This is all entirely normal!

The drogue parachute opened, sending the capsule – and the three of us – into a wild gyration as though we were on the end of a towel being vigorously waved in every direction. After about thirty seconds, things settled down. Then, the main chute opened and the wild gyrations started all over again. “It’s like a wild American amusement park ride,” shouted Andrey in Russian. I simply shouted “Yoo Hoo!”

Seat Cocking

To help absorb the shock of landing, explosive charges fired and instantly pushed our seats forward so that our faces were very close to the instrument panel. Window covers were jettisoned, removing the burnt opaque layer on the exterior of our windows, allowing light to flood into the cockpit, and providing an unobstructed view of the Kazakh steppes rushing up to meet us.

We could hear the rescue helicopters calling our altitude, and instructing us to prepare for landing. I raised my right arm so that I could see the window in my wrist mirror, and watched as the ground rose up.

I heard the “soft” landing rockets fire 6/10 of a second before impact. The actual impact with the ground was significantly harder than I anticipated. I remember thinking, “Wow that was hard, I’m glad that’s over.”  Little did I know we had a few landings to go!

On Earth

I knew that after landing we might have the sensation of tumbling because of changes to our vestibular system (balance) following a long mission in space. Debris being tossed around INSIDE the capsule was a solid sign we were really tumbling. The capsule finally came to rest on its side, with me on the bottom. The view from my window was dirt and grass. Earth.

Sunshine

Shortly after landing, Russian ground personnel opened the hatch, extracting Sasha from the capsule. I was next, followed by Andrey. The three of us were carried to reclining chairs, where we were able to speak to our families via satellite phone while the medical tent was being set up.  It was wonderful to speak with my family in Houston while we were all on the same planet, and it was really great to feel the cool breeze and warm sun on my face for the first time in 164 days.

After moving to the medical tent, I changed from my spacesuit into a more comfortable flight suit, while being checked out by Dr. Steve Gilmore and our NASA medical personnel.  After we were all checked out, Sasha, Andrey and I left the landing site in three separate helicopters for a ninety-minute ride to Karaganda airport. I took a nap.

Tradition and Farewell

We were welcomed at the airport by officials and young people, who presented each of us with flowers, chocolates, hand painted dolls and traditional Kazakh robes, which we wore during the press conference that followed. Then, after nearly three years of training together and sharing a mission during this milestone fiftieth year of human spaceflight, Sasha, Andrey and I said farewell, and then continued on our respective journeys home.

My journey home to Houston began when I boarded a NASA aircraft. The first stop was for refueling in Prestwick, Scotland. I was glued to the window on final approach as the lush green countryside passed below us. It was great to get out and walk around in the fresh Scottish air before continuing to Bangor, Maine in the United States.

As we approached the airport in Maine, we were treated to a stunning sunset. I sat there contemplating the difference between this sunset and the countless orbital sunsets I watched during my stay on the ISS. Besides the realization that I would see only one sunset each day, instead of sixteen, I really noticed the differences in the colors and the thickness in the bands of sunset.  As we waited for the aircraft to be refueled, I had the chance to speak with some Marine Corps V-22 pilots also waiting for fuel, and to let family know I was back in the U.S.

Home

I slept for almost the entire last leg of our flight, awakened by the sound of the flaps being lowered in preparation for landing at Ellington Field in Houston.  The landing was smooth and uneventful. My wife and three sons boarded the plane. I was truly home.

Paper Models 101

By Jim Gerard, INSPIRE Education Specialist, KSC, FL


Each month the INSPIRE Online Learning Community will feature a model of a NASA space probe, spacecraft, or aircraft. These models are intended to provide you a hand’s on experience with the engineering that went into the development and construction of these vehicles. While scale models are often simpler by design, it is easier to understand the systems and sub-systems that comprise the prototype. To make construction of these models available to the widest audience of students, they are designed to be printed on paper, cut out and assembled.

Tools for building paper models

Getting Started
If you have never constructed a paper model before, there may be some challenges. Prepare yourself by having the necessary tools at hand. Here is my list of tools:
• Sharp scissors
• Hobby knife (X-Acto good)
• Dull knife
• Metal straightedge
• White glue
• Toothpicks
• Tweezers
• Pencil (round preferred)
• Clear tape
• Work surface
• Cardstock
Make sure you have enough room to work and to leave items while glue is drying. Your work surface could be a wood or cardboard sheet about two square feet in size. I usually cut out a side of a mailer box, and have even used an old phone book. You just need something to protect your table while you are using the knife and straightedge.

Some notes on some of the tools: the dull knife can be an old hobby knife. I took an old one and scraped it on the concrete until it can no longer cut paper. It is used to produce straight sharp creases when you make folds. Toothpicks are used to apply glue. The pencil can be used to put a curve into the paper for making tubes and such, as well as marking items.

While you can use regular paper to print your model, I prefer to use cardstock. It is usually found at office supply stores and is marked as 60# weight. It is about as thick as a file card and gives the model a little more heft. Because of the extra thickness, I print one page at a time to keep it from binding in the printer, but your printer may handle it. Printing in color provides a better model, but black and white is OK. Once you have the model (and instructions!) printed and your tools assembled, you are ready to begin.

First Things First
Before making your first cut, read the instructions. Match up each step with the printed item so you know where they are and try to understand how things go together. This helps later as you have a better sense of why you are doing things in the order you are.

Before you make a cut, check to see where folds must be made. Use the straightedge and dull knife to score along these fold lines (usually marked with dashed or dotted lines). It is easier to score these before you cut them out, but can always be done after if you miss one. Some will suggest you should score valley fold (folding toward you) from the front and mountain folds (folding away from you) from the back, but I usually do everything from the front and it seems to work.

Carefully begin cutting out the items needed for your first assembly step. Long, straight edges can be cut with the sharp knife and straightedge. The knife is also good for very small cuts. For everything else, use the scissors. Cut everything you will need to complete the first step. Make folds where needed, and curve items by wrapping them around the pencil.

Stick to It

With the pieces required for the first assembly step all cut and folded, it is read to begin to glue them together. Always, always, always test fit before applying the first drop of glue. You may need to trim a tab or increase the size of a slot, and it is a lot easier to do this without glue on it. Once satisfied with the fit, it is ready to apply glue.

I make a practice to never apply glue directly from the bottle. An exception to this is if a large area, such as in the formation of a cylinder, must be glued. Instead, squeeze a bead of glue out on a scrap of card stock, and use a toothpick to transfer a small amount to the part to be glued. Here is the objective: to completely cover the intended area with as little glue as possible. Use the toothpick to squeegee off excess glue. Spread it to the edges. I often put some glue on the edge of the item I am gluing the part to to create a nice seam. Using a minimal amount of glue saves time on setting, and prevents a wrinkled appearance if the paper becomes wet with glue.

Once glued, slight pressure is applied until the glue sets. Sometimes it is just a matter of hold the parts in your finger for a few seconds. For larger items, I use clothespins and/or rubber bands (not too tight or you’ll crush the cardstock!).
If the item is large enough you may also use clear tape on the inside to hold parts together until set.

Whoops!

Inevitably, mistakes will occur. Fortunately they are usually easy to repair. If you make a cutting error, you can glue a small scrap of paper to the back to mend it. Miss a step and forget to glue something inside? See where you can cut it open and then fix the cut. Really mess up and make a crucial mistake? Just print out new parts and start again.

Sometimes starting over is the best remedy to a poor model. With foreknowledge of the processes you will do a much better job. You may decide to do some of your own engineering and add reinforcements for strength, or add extra detail. Hopefully, your completed model will be satisfactory to your tastes.

Gravity Probe B

Displaying Your Model

Once complete, you will want to show off your model. Most models are fragile and should be handled very carefully if at all. Prepare an area on a shelf or bookcase that you can use to set you model. Most of the models we present are spacecraft and look great hanging from the ceiling. Use fishing line or thread: tape one end to the model at the center of balance and wrap the other end around a thumbtack to push in the ceiling. Adjust the length of thread to avoid people walking into it.

Don’t forget to take a picture of your model when complete. You can take a picture just holding it or on display. We don’t count for skill, so don’t worry if you don’t think it looks quite right. The points we award are for the time and effort as well as the learning of the engineering makeup of the models. If you do your best, and follow some of these hints and tips, you should have a model you can be proud to share with your friends, your family and the Online Learning Community. Happy modeling!

LiveChat Roundup: Sept. 22

By Jim Gerard, INSPIRE Education Specialist, KSC, FL

A simple experiment:  a star, a telescope, and a spinning ball.  So simple, it took 40 years to come to fruition.  This was the description of the Gravity Probe B mission as described during our LiveChat by Jeffery Kolodziejchek and Tony Lyons of Marshall Space Flight Center.  105 OLC members participated in the chat, which included a brief history of time-space theories and the nature of gravity.

Gravity Probe B used a precision pointing telescope to measure the effect of gravity on the most precise gyroscopes ever constructed.  Measuring the change in these gyros enabled physicists to verify some of Einstein’s predictions on the effect of a large mass (in this case the planet Earth) on the space-time continuum.  Our presenters only had time to highlight the mission and its findings, but have provided much more information in their presentation.  You can download a PDF of the entire presentation including the extra slides from the Discussion Board.

If you missed this great chat, remember you can download it from the archive.  Three versions are made available, usually by the following Monday.  You can download a Collaborate file that opens up and plays in the same chat window we use for our live event.  Or you can download it as a Quicktime or MP3 file that can be viewed or heard on a pad or smartphone.  As always, note the password given at the end of the presentation to access the quiz for your points.

Next week, our INSPIRE team will be meeting in Orlando to discuss and plan for our next year of the OLC and Summer STEM Experiences, but we will still have a chat on Thursday!  Sign up now to hear Dave Seal of the Jet Propulsion Laboratory chat about planning the course of our space probes to the planets.  See you then!

P.S.  Have you built the Gravity Probe B paper model?  Stay tuned on Monday for some hints and tips on building paper models, as well as pictures of my completed GP-B!

Discuss this blog 

LiveChat Roundup 9-20

By Jim Gerard, INSPIRE Education Specialist, KSC, FL

No, our LiveChat was not early this week!  We still have our regular event on Thursday night at 8:00pm CT.  But we have had many students ask if they could be held at different times and dates.  We feel it is important to have a regular event the whole OLC can depend on, but want to offer some additional chats others may join.  So occasionally there will be an additional chat offered.  It will have its own sign up area on the Discussion Board, and will vary in time and day offered.  On Tuesday we had one of these special LiveChats on our featured NASA Center, the Ames Research Center.

64 participants heard about the ARC from K-12 Education Specialist Jonas Dino.  Mr. Dino gave a brief history of ARC (did you know it was older then NASA?) and then highlighted many of the different missions that are directed by ARC.  One of these is the development of air flight management techniques that will provide safer more speedy service.  Check out this video that shows total flights across the US during a single 24 hour period:

http://quest.arc.nasa.gov/projects/smart_skies/mov/24hrs.html 

We had lots and lots of questions, so many that we ran out of time.  These extra questions were sent to Mr. Dino to be answered off line.  I’ll post them here when they are ready.

Thursday, we will have our regular LiveChat with Jeffery Kolodziejczak and Tony Lyons of Marshall Space Flight Center.  He’ll talk about the Gravity Probe B which helped confirm Einstein’s theory of gravity.  Our participant limit has been reached, so if you did not get a chance to sign up plan on viewing the event in the archive. 

J-2X Progress: Engine 10001 Testing Status

By William Greene, MSFC, AL

When last I discussed with y’all the status of testing on the first J-2X development engine, E10001, I showed you a video of our first mainstage test, A2J003. That article was posted just over a month ago. So, what's been happening since then? Hopefully, this brief article will catch you up to where we are.

First, we had test A2J004 in early August. This test went the full, planned duration of 7 seconds. This was our first test with any sustained duration at mainstage conditions. Lots and lots of good data. The Datadogs and the analysts were absolutely giddy for days and days afterwards.

We then had test A2J005 in mid August. This test was scheduled for 50 seconds duration but it was cut off at 32.2 seconds due to a not-totally-unexpected redline cut. This redline cut was similar to the one described for A2J003. In fact, it was the same parameter although the test conditions were different. You can stomp your foot, or kick at the air, moan, whine, whatever; it doesn't really make any difference (…which is not to say that we did any of this … well, okay, maybe a little whining…). This is all simply part of the learning process with a new engine. It is expected, necessary, and educational. Deep breath and all is well.

Here is a video of test A2J005: J-2X Fifty Second Test

However, after test A2J005 shutdown -- several seconds after shutdown -- we had a "pop." These are not uncommon when ground testing rocket engines so let me use yet another automobile analogy (since I use them so often) to explain.

Just a few years ago, I was still driving my 19-year-old pickup that I bought just before grad school. Towards the end of its long and glorious life, my little red truck developed a habit of rumbling and grumbling to a stop long after I'd turned the key to "off." Residual gasoline fumes and air and hot metal combined into a sequence of "blurrr, blurrr, cough, cough, blurrr … POP" (and the neighbors just loved that!). In essence, a similar thing happened on A2J005.

In flight, the shutdown environments are quite different than on the ground. When you're way, way up in the atmosphere -- or even outside of the atmosphere -- the surrounding environment is effectively a vacuum, which is a very useful means of sucking out any residual propellants from the engine after shutdown. On the ground, residual stuff (leftover propellants and fuel-rich combustion products) doesn't get pulled out as efficiently. We can and do push it out with inert gas purges, but they're not always as effective as we'd like. And so, on A2J005, we didn't get everything pushed out as well as we'd like and we had a "pop" -- or, actually, a "POP." Technically speaking, it was a detonation in the "lox dome," i.e., the oxidizer manifold volume feeding the main injector.

The bottom line is that we had some damage. It wasn't anything that couldn't be fixed and so, we're fixing it. We didn't bend any metal or anything like that. It's more of breaking something that's kind of like really tough plastic. Throughout this article you'll see pictures of the engine being pulled out of the test stand because we couldn't do the repair in place. After removal, we then took the engine back across the NASA Stennis Space Center to the assembly facility. In other words, we took it back to the garage for a tune up and we'll be back in business soon. In fact, E10001 will be reinstalled by mid-September and we'll be back into testing right around the start of October. Oh, and we'll be doing a better job of avoiding pops based on what we've learned about purge rates and durations.

So, that's where we stand. Two things to look forward to in the future: first, the upcoming report on test A2J006 after it happens, and, second, a discussion of another change we made to the engine while we had it in the shop. That latter discussion is an interesting technical tidbit regarding the internals of turbomachinery. So, "Don't touch that dial!" and keep your set tuned to this station…

(I think that my grandparents had this exact set! Ahh, the good old days of vacuum tubes and horizontal hold.)

Comment on Discussion Board

Live Chat Roundup: Sept. 13

By Jim Gerard, INSPIRE Education Specialist, KSC, FL

We hosted a special Tuesday edition of the Live Chat, specifically for those who were coming into INSPIRE for the first time (although a few returning members were welcome!).  67 students participated, with a pretty even mix of class levels.

The chat explained the use of the Elluminate chat system, and gave students a heads up on signing up for and being part of our Live Chats with NASA subject matter experts.  We then shared a browser to look over the Online Learning Community, explaining the parts and where to find important information.  With all of this, we had very little time for questions and answers, so I asked all students with questions in the queue to send them to me.  Here they are, followed by the answers.

David asked: Are we required to complete all of the activities?
INSPIRE: Definitely not!  We know there are a lot of different interests in the community, so we post a lot of material in the hope you will find something that interests you.  You don't have to do it all!

Ethan asked: When do registration for live chats typically open up? For example, one week before, two weeks before, etc.
INSPIRE: We usually have a week to sign up, to avoid confusion and to give more an opportunity to be part of the live event.  So sign up usually runs from Friday to Thursday for the Thursday night chat.  An exception is when we have a special chat on Tuesday.  We might open that earlier than a week ahead, and will announce it in the eINSPIRE newsletter.

Josephine asked: Has participating in the INSPIRE program already been added to our college applications?
INSPIRE: No, you will need to include that as you apply.

Bhavna asked: Do we receive points for attending these chats? I mean points that go towards our applications for the Summer STEM program next year?
INSPIRE: You don't get points for attending the chats, but by taking a short quiz afterward.  The quiz is password protected, and you get the password from the chat.  Taking the quiz allows the points to be awarded automatically.

Lauren asked: In the points area on the OLC, there is a category that says LiveChat. Do we get points for participating in this and other chats?
INSPIRE: See above!

Chandler asked: How long do messages stay on the Discussion board? Are they auto deleated? Or all manualy deleated? It just seams like it might get crowded with messages after a while.
INSPIRE: Messages remain on the DB for the whole year.  As you suggest, it can get crowded, but you can sort by latest message so all the old ones are 'in the back', or use the option 'Unread Messages Only'.  We can give some more DB tips in another blog.

Nicholas  asked: What are the different ways to earn points? Do the paper models earn points?
INSPIRE: Yes, paper models will earn points! At the very bottom of the Discover page, you can click to a chart showing point breakdowns and Leaderboard levels.  This gives a good overview of the different things you can do.

Kristopher asked: Will the chosen patch be available to students as a fabric patch?
INSPIRE: In the past, all students have received a sticker of the patch.  We do make some cloth patches but we are unable to provide one to every student.  Maybe advancing on the Leaderboard may yield some type of award?

David asked: How much time do I have to complete the current activities/assignments?
INSPIRE: Activities are always available, but some things (like some challenges and competitions) have due dates.  If there is a deadline, it will be prominently mentioned.

Alex asked: I haven't made a paper model before. Does it take a specific stronger type of paper? And do you have any tips on how to make them? Plus... are there directions for making the Gravity Probe B model for the activity?
INSPIRE: I always use card stock (I think it called 60 weight at the office supply store), but you could use regular paper (though things may droop a bit!).  I'll post a blog this week on tips to building paper models, but basically, take your time and read the directions.  All models have directions attached (I print out the directions on regular paper).

Bradley asked: Typically how many challenges or activities are there in a month?
INSPIRE: One big activity and 5 to 8 smaller ones, and then we have long term activities like the ISS Science Challenge which will run all year.

Meron asked: Are the activities scaled to some degree for different levels of prior knowledge?
INSPIRE: We offer many different levels, so if you find one too difficult, try another one.  You can always go back and do it later.  BTW, we give unlimited attempts on the quiz, and only keep the higher score, so if you poorly, have another go at it!

Caroline asked: How valuable are points toward applying for the summer internship?
INSPIRE: You may need a certain point level to open the application window.  We'll announce that soon.

Isabella asked: What is the funnest activity of the year?
INSPIRE: (Teacher voice) It is the activity that brings YOU the most enjoyment!(/Teacher voice)
(Mr. Gerard voice) I like the paper models, and will be building them with you all during the month they are presented!

Thanks for all these questions!  If you were unable to participate in the live event, you can check it out in the Live Chat Archive (and get points for the quiz)!

Respond on the Discussion Board

Inside The J-2X Doghouse: Engine Control -- Open versus Closed Loop

By William Greene, MSFC

As I was driving to work this morning, I came up over a rise and saw suddenly appear in my windshield, over towards the left on the other side of the road, a police cruiser with a radar gun mounted in the window.  Even before I could think about it, the pressure of my right foot on the accelerator lessened.  I then instinctively looked at the speedometer and found that I was traveling 48 miles per hour on a road for which the speed limit is 45 mph.  Thankfully, the officer apparently forgave me the 3 mph violation and continued to wait where he was for a better opportunity to serve and protect the community.

What I find interesting about that little episode was the immediate, unthinking response I made in response to seeing the cruiser.  In terms of control systems, that could be called a feedback loop.  My senses received data, my brain rapidly processed that data and then sent a signal to react to the data, and then my calf muscles responded by easing up on the throttle.  The car, in turn, slowed to respond to the lower throttle.  Never mind, of course, that if I'd been really, really speeding all this would have been too late (and I would have arrived at work very angry), there was nevertheless a closed-loop response that is not too dissimilar to what we do for rocket engine control … in some cases.

First, let's get familiar with a couple of terms –

Open-loop: We typically refer to something as open-loop when we have instrumentation that measures conditions in the engine but the engine itself does not respond to those measurements.

Closed-loop: We typically refer to something as closed-loop when we have instrumentation that measures conditions in the engine and then, potentially, the engine takes action based upon those measurements.

It is based upon those definitions that I would call my response to seeing the cruiser closed-loop since I responded and did something with the data.  Another example would be the more modern systems that are used to monitor and control automobile systems.  It used to be that you had a temperature measurement stuck in the coolant loop.  You could watch the temperature rise, but until the system went kaput and boiled over leaving you stranded alongside the road, there was no active, closed-loop control.  Nowadays, if the computer in my pickup truck sees that the engine temperature is too high, it will take action to try and protect itself.  For example, it will inhibit the use of the air conditioning system since that represents an additional power requirement on the engine.

 So, what do we control on a rocket engine?

One thing that we control is power level.  On the Space Shuttle Main Engine (SSME), power level is controlled in a closed-loop manner.  This means that the main combustion chamber pressure is measured as an indication of thrust level and in response to that measurement a valve is opened or closed to increase or decrease the engine power level.  On the J-2X, power level is controlled in an open-loop manner.  This means that we measure the main combustion chamber pressure but we don't have any feedback loop where we control a valve to ensure that we're on target.  Instead, should we happen to be off on power level, we have to physically change an orifice in the engine between tests.  The "feedback loop" is data analysis and a guy with a wrench.  Which approach you choose to take are dependent upon your requirements of performance and affordability.

Another thing that we control on a rocket engine is the mixture ratio (i.e., the ratio of oxidizer to fuel).  Given that on a rocket you are carrying both your oxidizer and fuel with you in the vehicle, you certainly want to make sure that you consume your propellants in the correct ratio to get the most uumph out of them.  Again, on SSME we control mixture ratio in a closed loop manner.  There is actually a small flowmeter on the SSME and, using the data from that flowmeter (and some associated calculations), we move a valve on the engine to dial in the correct mixture ratio.  It's a pretty nifty system.  Also again, on the J-2X, we have an open-loop system for mixture ratio just like we have for power level.  We test the engine, look at the results, and, if necessary, make a physical change to the engine in the form of an orifice.

Because of these two areas, power level and mixture ratio, SSME is usually referred to as a "closed-loop engine" and J-2X is usually referred to as an "open-loop engine."  Now, this terminology is not entirely correct since there are some closed feedback loops within the J-2X control system pertaining to engine health and status diagnostics, but we all know how enduring shorthand designations can be.  Also, engines don't have to be one or the other.  They can be half-and-half.  The engine used on the Delta IV vehicle, the RS-68, sort of falls in this category.

How you choose to design your engine control system is driven by your requirements.  Put real simply:  The SSME is all fancy-schmancy because it had extremely tight power level and mixture ratio precision requirements and because it was a reusable engine.  The J-2X is intentionally more simplistic because it has looser precision requirements and because it is expendable (and throwing away orifices is a whole lot cheaper than throwing away valves if your requirements will let you get away with it).  Requirements drive design.

Note that I will save the fun topic of engine diagnostics -- and the potential for long philosophical meanderings within that realm -- for future posting.

Let's end this posting with a fun little exercise.  Above is a simplified schematic of a gas-generator cycle engine kind of like a J-2X.  I have shown in the schematic two orifices #1 and #2 (highlighted in yellow).  With those two orifices, we can calibrate the engine.

Scenario:  Power level too low, i.e., measured main combustion chamber pressure too low.

• Solution:  Increase the size of orifice #1.
• Explanation:  By increasing the size of orifice #1, I will deliver more oxidizer to the gas generator.  This will deliver more power to both turbines thereby increasing how much propellant gets pumped into the engine.  More propellants pumped in equals more thrust and greater overall power level.

Scenario: Power level too high, i.e., measured main combustion chamber pressure too high.

• Solution:  Decrease the size of orifice #1.
• Explanation:  The exact opposite of the previous scenario.

Scenario:  Mixture ratio too low, i.e., the flow of oxidizer is too low in proportion to the flow of fuel, as measured by the test facility.

• Solution:  Decrease the size of orifice #2 and decrease size of orifice #1.
• Explanation:  By decreasing the size of orifice #2, I decrease the amount of flow that is diverted around the oxidizer turbopump turbine.  I therefore increase the flow through the turbine thereby increasing pumping power of the oxidizer side.  So I increase oxidizer flow to the engine.  However, by increasing oxidizer flow to the engine and doing nothing else, I've probably messed up my overall engine power level so I've got to back down a little bit by decreasing the size of orifice #1.

Scenario:  Mixture ratio too high, i.e., the flow of oxidizer is too high in proportion to the flow of fuel, as measured by the test facility.

• Solution:  Increase the size of orifice #2 and increase size of orifice #1.
• Explanation:  The opposite of the rationale for the scenario immediately above.

See, being a rocket scientist isn't that difficult, really.  Now you too can calibrate an open-loop rocket engine.

P.S., I read in the paper this morning that NASCAR racer Kyle Busch had his civilian driver's license revoked for 45 days for doing 128 mph in a 45 mph zone.  Well, at least I wasn’t going that fast when I came over the rise this morning and saw the police cruiser.  Then again, I wasn't driving a $400,000 Lexus LFA sports car like Mr. Busch was…

Read more blogs about the J-2X engine development.

J-2X Doghouse: Okay, So We Ain't That Smart -- Yet

By William Greene, MSFC

Welcome back to the J-2X Doghouse.  We're going talk about some test results and test data, exactly what Data Dogs love most to do.

Back in the day -- back before I had the carefully regulated, federally mandated, and strictly enforced lobotomy that allows people into the ranks of management -- I was once an analyst.  And, since it seems so long ago that it doesn't sound like bragging anymore, I will admit that I was pretty good at it.  I absolutely loved the process of using fundamental physics or empirical correlations for fluid dynamics, thermodynamics, and heat transfer all together to simulate in computer coding how things function in the real world.  Whereas many people enter the field engineering because they like mechanical things or electronic things, there are some of us who relish the seeming purity of problem solving in abstraction.

 Over the years, working on many diverse projects and building many diverse mathematical models to simulate many diverse systems, I came to the realization that my models always appeared most unassailable and brilliant when there was no test data against which to compare them.  To put it bluntly, test data always proves that you simply ain't as smart as you thought you were.  But, that's okay.  If that wasn't the case, then you wouldn’t bother to test.  The whole point of testing to gather data and learn more.

With all due respect to the Serenity Prayer, this ought to be the analyst's prayer relative to testing:

Grant me --
-- the results to validate that which I do understand
-- the data to explain that which I did not understand
-- and the openness to accept that I can always understand better

That last line is critical.  Ignoring data contrary to what your model output is a seductive, addictive, and dangerous path to follow.  We don't/won't do that.

That brings us to the subject of test A2J003 of the J-2X development engine E10001.  This was our first test to mainstage operation.  The planned duration was to be seven seconds.  On Tuesday 26 July, right around five in the afternoon, the test ran for 3.72 seconds and then shutdown.  We did not accomplish the full duration.  Why?  Basically because we ain't as smart as we thought we were.  We had analytical models telling us that performance would be X, but the hardware knew better and decided on its own to perform to Y.  Here is a cool video of the test:

J-2X Engine Test A2J003

A more detailed explanation of what happened is that the engine shutdown due to the measurement of a pressure too high in the main combustion chamber.  The measurement crossed a pre-set "redline" and the test controller unit took the automatic (and autonomous) action of shutting down the engine in a safe and controlled manner.  The high pressure in the main chamber was caused by higher than expected power coming out of the oxidizer pump.  This, in turn, was due to more power being delivered to the turbine side than expected.  It comes down to a fluid dynamics phenomenon (pressure drops) and what we have is not inherently bad, just different than expected.  So, in essence, we used our models to predict that the pressure in the main chamber would be at a certain level -- indicating a certain power level -- but the different performance of the hardware resulted in pushing us away from our analytical prediction.

• Here is the good part:  We learned something.  We learned that our model needs to be updated and we collected the data that will allow that to happen.
• Here is another good part:  We got enough data, despite the short duration, to recalibrate the engine for the next test thereby making it far more likely that we will hit our target. .
• Here is yet another good part:  We had a successful demonstration of the test controller redline system by safely shutting down the engine.  The engine looks fine.  The controller did exactly what it was supposed to do and protected the hardware.  In fact, for these early tests we have the redlines clamped down pretty tight specifically to protect the hardware as we learn more about the engine..
• And here is, finally, yet another good part:  Other than the power applied to the oxidizer turbopump, most of our other predictions with regards to hardware performance appear to be awfully darn good.  So, we've got a preliminary validation for much of our understanding of the engine.  Indeed, this is a brand new engine and we have just accomplished mainstage operation in the second hot-fire test.  That is truly unprecedented..
• Here is the bad part: We have to spend a few minutes explaining to folks not directly involved that despite not achieving full duration, the test was in reality a total success.

If that, then, is the bad part, I can live with it.  I can live with admitting that we ain't as smart as we thought were.  Why?  Because now, after the test, we are indeed smarter.  And we will continue to get smarter and smarter about the J-2X design until, one day, we will be smart enough to say that, yes, we understand this engine so well that it is safe enough to propel humans into space.

Read more blogs about the J-2X engine development.

Welcome to the 2011-2012 Online Learning Community!

By Jim Gerard, INSPIRE Education Specialist. KSC, FL

 

Welcome to a new year of the INSPIRE Online Learning Community!  If you are new, take some time to poke around and explore the different parts of the OLC.  The Discover page will post activities to do and challenges to team up for, Connect will be a virtual meeting place with other INSPIRE students and NASA, and Equip will provide resources for school and university selection. Returning students will notice a new look to the OLC, so you also should reacquaint yourself with the location of your favorite areas.

A change that returning students will notice is a change in the structure of our points and the way to earn them.  Each month will have a new theme, with weekly sub-themes.  A big activity based on that theme will challenge you to learn and report out in a creative way.  Short activities will change each month, and be automatically scored.  A long term learning experience called Modules will provide in depth insight into a science or math subject.  And, if you enjoy building things, try the monthly model and construct a collection of space vehicles!

To learn more about the OLC and what is in store for this year, sign up for our first Live Chat.  It will take place Tuesday, September 13 at 8pm CT (all times on the OLC are listed as Central Time: make sure to adjust for your own time zone!).  Sign up is open on the Discussion Board and limited to the first 100 students.  If you are too late to sign up for the live event, watch it Monday morning in the OLC archive!

Discuss on the Discussion Board

A Beautiful Disaster

By Mike Fossum, ISS Expedition 28/29

We’ve been watching Hurricane Irene take shape as we’ve flown overhead the last few days.  I took this picture as she was clearing the Caribbean and pressing toward the Carolinas on Friday afternoon. Stunning. And scary.

When I look down from my vantage point on the space station, most of the time I marvel at the complexity and beauty of our home planet. We mostly look for bits of brown and green (i.e., land) on an otherwise blue and white tapestry of ocean and clouds. In fairness, you can sometimes see traces of ocean currents and mildly interesting patterns in the clouds, but those just don’t draw my attention like the land with its mountains, rivers, fields, and pallet of colors.

This week I watched a mildly interesting circular pattern of clouds turn into a fearsome storm. I may never look at clouds with marginal interest again.
After living on the Texas Gulf Coast for most of my life and experiencing the raw power of several hurricanes first-hand, this sight of a full-blown hurricane evokes a lot of emotions.

Good luck down there!
You’re in our thoughts and prayers up here!!

Living the Dream!