Stennis Space Center – Page 2 – Liquid Rocket Engines (J-2X, RS-25, general)

J-2X Progress: Mission-Duration Test

Five hundred seconds is exactly eight minutes and twenty seconds. Nope, that’s not rocket science. But that was what I had to keep in mind as I watched the stopwatch application on my smart phone during the last J-2X test. Eight minutes and twenty seconds. That seems like a really long time when you’re counting every second.

Let me set the scene.

At the NASA Stennis Space center you have collected the directors from seven of the ten NASA field centers around the country. You have representatives from the NASA headquarters in Washington, DC. You have a live feed being picked up by NASA TV and broadcast into the living rooms of thousands or millions of dedicated NASA TV junkies. You have dignitaries in suits and technicians and test conductors in jeans and Hawaiian shirts (test-day tradition), reporters with notepads and cameras from every paper and television station in the greater New Orleans and southern Mississippi area, and, sitting in his ceremonial throne, the Grand High Exalted Mystic Ruler of the International Order of Friendly Sons of the Raccoons.

Well, okay, that last part about the Exalted Mystic Ruler is just fictional (bonus points to anyone who gets the 20th-century cultural allusion without Google help), but that’s the way that it felt. This was test A2J008, the seventh planned hot-fire test of the very first development engine and it was time to play show-and-tell.

Does everyone remember show-and-tell in elementary school? You bring in something that you think is neato or special and, by getting up in front of class and talking about it you reveal something about yourself and you accidentally practice public speaking and presentation. Once, when I was seven years old, I brought in my new baby brother, or, well, my mother did so at my behest. I wish that I could remember what I said about him. I imagine it was something like, “He’s short, cranky, and smells funny.” Today, at least he can say, he’s taller than me.

J-2X is our new baby brother — of a sort to carry forward the analogy — and we’re showing him off to the world. Through the first six hot fire tests of engine E10001, we accumulated a total of 225 seconds of test time. For test A2J008, on November 9th, our show-and-tell for the world, we scheduled a test lasting 500 seconds, which is the mission duration requirement for the engine. Here is what I saw during the test, while holding the stopwatch, standing out in the field in front of the test control center:

Can’t see anything? Okay, I’ll expand the picture in pieces starting on the left.

This is the hydrogen burn stack. All of the excess hydrogen coming from the facility or from the engine before, during, and after the test needs to be burned off. This is all bleed flows and waste flows that you cannot avoid when dealing with a cryogenic propellant. If you let hydrogen accumulate anywhere around the facility, then “BOOM” you’re eventually going to have an explosion. Talk to the guys who work out in the test areas and they’ll tell you plenty of tales of such things. What is amazing as you’re standing out in that field to watch the test is the radiation heat coming off that thing. It was a chilly day and yet you almost feel like you’re going to end up with a sun-tanned face. It feels like the sun while you’re on the beach except that as warm is it makes your front side, your back side is still chilly from the blustery November breeze. Kind of an odd sensation being both overheated and chilly at the same time.

In the middle of the picture is a sign for anyone who was born without that instinctual reflex for self-preservation. While it would seem obvious to me to not walk in front of a roaring rocket engine throwing out a plume reaching hundreds of feet in the air, the fact that they have a sign like this suggests to me that for someone, somewhere, at some time, this was not so obvious. An unfortunate thought…

And, on the right-hand side of the picture, in the distance, is test stand A-2 with the engine firing. In the middle of the picture below, there is a tiny, very white spot in the middle of the test stand. That’s the flame coming directly out of the engine nozzle. In the bottom right corner of the picture below you can just see the edge of one of the liquid hydrogen barges. For both liquid oxygen and liquid hydrogen, for extended duration tests, the propellant tanks on the test stand are not quite big enough to hold all of the necessary propellant. So, during the test you actually transfer propellants from these barges into the test stand tanks. So, the engine is draining the test stand tanks while you are simultaneously re-filling them from the barges. With all of this going on, you start to appreciate the coordination necessary to pull off one of these tests.

When you’re standing there being halfway cooked by the burn stack, several hundred feet away, the roar from the engine is nearly deafening. Many people wear hearing protection. Others of us are aging rock-n-roll fans. I honestly don’t think that anyone gets a complete sense of how powerful these machines are until they see, hear, and feel one of these tests. All of the performance numbers in the world simply do not have the same visceral impact as when the engine lights and the initial sound wave runs over, around, and through you and you watch the flame bucket fill with billowing, thick, white steam. Even twenty years after having seen my first test in person, I still cannot help but stand there like a bedazzled goof and say to myself, “Wow.”

Here, below, is a picture of the test from the other side of the stand. Why is this important (other than the sign on the fence clearly advertising what you’re looking at)? Because this is the side from which all of the non-NASA folks, some of the NASA dignitaries as well – including an astronaut representative – and the local press corps watched the test.

So as to not keep you in any more suspense, the test came off perfectly. The full, planned duration of 500 seconds was achieved thereby effectively tripling out test experience to date. The coverage on NASA TV was good. The bigwigs clapped and cheered with infectious excitement right along the rest of us. And the press corps wore out their thesauruses trying to capture just a slice of the actual experience. It was a complete success on all fronts.

Congratulations to the Pratt & Whitney Rocketdyne J-2X development team, the NASA SSC test crew, and the NASA Marshall Space Flight Center project management team. While I had every bit of confidence that we’d be successful, with so many people watching our show-and-tell exercise, those 500 seconds — eight minutes and twenty seconds — ticking away on my stopwatch seemed like a whole lot longer. Whew! and Yahoo!

J-2X Progress: Engine 10001 Testing Status

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.)

J-2X Progress: Pardon Me

I’ve lived in the South for about 20 years now. Over that time, I’ve heard and learned all kinds of quirks of regional dialect and colloquial sayings. I’m quite sure that I’ve even picked up a few myself. Oh well. One particular expression shared with me by a former training partner in the gym was a compliment. She told me that I had good “home training.” That is a shorthand way of saying that my parents taught me to have good manner.

With that in mind, and in consideration of what we’ve been calling the first hot-fire test of J-2X development engine E10001 (i.e., the “burp test”), I respectfully and bashfully declare:

In the early evening of Thursday, 14 July, E10001 generated a burst of ignition and thrust with something like a 30,000 pounds of force — enough to toss five or six crew-cab pickup trucks into the air. That’s one heck of a burp. Yep, we were successful. NASA Stennis Space Center in Mississippi, coordinating with the Upper Stage Engine office at the NASA Marshall Space Flight Center and with Pratt & Whitney Rocketdyne in Los Angeles, California conducted a full-duration, 1.9-second test. Here is a picture of what a burp that big looks like:

Here are a couple of pictures of the engine prior to the test. These are taken from a deck inside the test stand basically looking down on the engine. The nozzle extends through the deck to the next level below.

You’ll note that there’s some misty fog hanging around the engine in those pictures. While it is true that most of the time you can almost see the thickly humid air of southern Mississippi in July, this is something different. This fog is being created by the presence of cryogenic propellants in the lines. These lines are so cold that they effectively condense water in the air around them, even at a distance, to create a fog. Here are some close-up frosty pics of lines chilled down prior to test:

Out of one end comes smoke and fire while the other end is frosty cold. This is a good illustration of the broad span of environments that exist within a rocket engine.

So, what’s next?

As exciting at this brief test was, what we didn’t do is light the gas generator and get the turbomachinery up to full speed. That’s the goal for the next test. In addition to spinning up the turbopumps with helium and lighting the propellants in the main chamber, as we did for the burp test, we’ll take the next step in the start sequence and light off the propellants in the gas generator. This will provide the turbopumps with the power necessary to reach mainstage, steady-state operation. And that — those initial few seconds of mainstage — will be our first glimpse at genuine engine operation like that which will propel spacecrafts into orbit and then outwards across our solar system.

J-2X Progress: The Burp Test

On my very first home computer, I had a silly little program — made by the marketers for the Monty Python brand name I believe — that turned the keyboard into collection of funny or disgusting or borderline obscene simulated sounds of bodily functions. Several keys triggered a variety of sneezing sounds. Another set of keys activated a broad range of burping sounds. Another set of keys set off sounds inappropriate for further discussion within a NASA blog. And, of course, there were handful of sounds that simply left you scratching your head. I guess that one should feel heartened by the notion that even at a time when the sterile realm of machines seem to be taking over our lives, we still revert to our childish fascination and amusement with the functions of our quirky bodies.

And so, in that light, I give to you the J-2X Burp Test. No, that is of course not the official name. The official name is the “J-2X Ignition Test” or, even more formally: Test A2J001. That really rolls off the tongue doesn’t it?

Etymological dissection of “A2J001”
     • “A2” because the test is happening on NASA Stennis Space Center test stand A-2.
     • “J” to distinguish this from 30 years of Space Shuttle Main Engine Testing data records related
        to test stand A-2.
     • “001” because, well, it’s the first test

The first test of the first J-2X development engine will have a duration of 1.9 seconds between the time that the engine receives a command to start and the time that the engine receives a command to shutdown. That is not a long time. It is, indeed, not a whole lot more than an extended, impolite belch considering that the engine is designed to ultimately roar for a full eight or ten minutes for full-duration tests.

So, why do such a seemingly silly little test? That’s a valid question and the answers back are just as valid. We have a wide range of objectives for this test. For example, this will be the first time that cryogenic propellants (liquid oxygen, liquid hydrogen) will have been loaded into the engine and the lowest reaches of the facility feedlines. Remember, these fluids are so cold that they make metal shrink. You have to design the engine and the facility to resist or accommodate this thermal stress. And while you continuously check for leaks as you assemble the engine and the facility, nothing is ever quite like a good cryogenic chill for finding where seals might separate.

Also, during a chill test you want to make sure that you can get the engine cold. I know that that sounds funny, but it is possible to have enough ambient heat going back into the metal of the hardware such that it overwhelms the capacity of the cold fluids to take it away. Essentially what happens is the cryogenic fluids boil when they hit warmer metal. Boil? Like water in a pot on the stove? Yes, but remember that liquid hydrogen boils at about 420 degrees below zero and liquid oxygen boils at about 300 degrees below zero (both Fahrenheit). What you want is for the hardware to get so cold that the boiling stops. This is accomplished by continuously flowing new, fresh, cold stuff through the hardware via a bleed line. During the chill test, you monitor the conditions within the engine and of the fluid coming out of the bleed line. When you get to a suitably cold, steady state situation, then you’ve successfully chilled the engine.

Why is this important? First, you run this test to make sure that you actually can chill the engine. Not only do you design the engine to run, you have to design it to be able to get to this chilled state during a launch sequence. Second, the engine needs to be chilled because if you have any boiling liquid in the pumps when it is time to start, that boiling represents voids in the fluid. The movement of the pump will exacerbate these voids and potentially convert even more of the liquid into gas. The pumps are not designed to pump gas and so the result is that the engine could go off mixture ratio, or it could fail to start, or it could even head rapidly towards a far more exciting failure situation. Like a good martini, really chilled is really good.

Next, after the long chill, like a long, filling meal, comes the … BURP …

The 1.9 ignition test will demonstrate: the use of the helium spin-start system, ignition of the augmented spark igniter and the main injector, and the functioning of the start continue logic software. Now, explaining one at a time —

In your automobile, you’ve got an electric motor that, when you turn the key (or push a button these days in some fancy cars), spins the motor to life. We’ve got essentially the same thing on the J-2X. There are different ways that this could be accomplished, but one of the cleanest and simplest is to use the inherent functionality of the turbines and provide a burst of power in the form of high-pressure helium. The helium flows through the turbines, spins up the pumps, and thereby builds pressure throughout the engine making it primed for the rest of the start sequence. The important features that will be demonstrated with the planned short test is the careful timing of the sequence and the tailoring of the pressure profile supplied to the turbines to yield the desired pressure build up on the other end, in the pumps.

The augmented spark igniter (ASI) is, effectively, a torch lit off by a pair of spark plugs. This small hydrogen-oxygen torch resides in the center of the main injector and it is what lights off the propellants in the main chamber during the start sequence. Just like you don’t start a campfire by holding a match against the biggest log in the pile, the ASI provides the kindling to get the main fire going. The burp test will demonstrate the effective discharging of our high-tech spark plugs and achieve ignition of the ASI and the main chamber. They will not be lit for long, but just long enough to characterize the process.

Just like everything these days, the J-2X and the entire test facility element are run by software. Streams of 1s and 0s are taking over everything. And while J-2X does not have an exceptionally complex control system, there are a handful of absolutely critical feedback loops that must function properly. The “start continue logic” is composed of a set of criteria that tell you, as the engine progresses through the start sequence, that it is okay to continue with the process. Being not “okay” in this case means that you could be facing a catastrophic situation and that you must halt the engine starting process in order to ensure safety (of the engine, of the test stand, and, in flight, of the vehicle and crew). Now, for this short test, it is extremely unlikely that we would be building up enough energy to damage much of anything even if things did go awry, but what is important is the demonstration of the closed loop of imposed software limits, measured parameters, the application of software logic, and the confirmation that all is well. Considering that the engine and test facility is being entirely controlled by a group of people in a secured building that is hundreds of yards away, making sure that you’ve got complete control of the test facility and test article, and complete insight into what’s going on via instrumentation, is pretty darn important.

So, that explains the strategy behind the first test of J-2X E10001. What we will not be doing is lighting the gas generator. That would be the next step in the start sequence: spin up the pumps, open the valves, light the main chamber, and then light the gas generator. We will then be just one step away from ramping up to full power. We’ll save that step for next test.

To be entirely frank, this first won’t be very impressive for uninvolved bystanders, it probably won’t even be as much fun for a lot of people as would be the silly/disgusting bodily function sounds on my very first computer, but for those of us down in details, this burp test is a vital full — dress rehearsal before the real fun begins of genuine, mainstage engine testing. It represents yet another significant milestone on our path towards completing J-2X development. Go J-2X!

J-2X Progress: Road Trip, Baby!

It wasn’t too many years ago that there was this thing about asking sports heroes after winning the big game, “So, what’s next?” They would always dutifully answer “I’m going to Disney World!” I guess that that whole thing is passé since I’ve not heard it in awhile, so I am going offer an alternative. Maybe it’ll catch on and be the BIG THING this summer…

…or, well, maybe not.

But that is what happens next. Our little engine is pulled out of the air-conditioned confines of its assembly area and trucked across the NASA Stennis Space Center to its test stand. No more pleasantly cool and dry air for you, E10001. This is Mississippi in June. Thus, in order to make this trip out in the open like this on the back of the truck (don’t try this at home!), the engine has to be sealed up tight against the humidity (and bugs) hanging in the air. Anywhere where there is an opening, there is a cover, a closure, or a plug. From the lot at the assembly building in picture (1) below, down the road towards the engine testing area in pictures (2) and (3), and finally arriving at the lot behind test stand A-2 in picture (4). In picture (5), you can see that the truck backs in alongside the test stand for the next operation.

The next operation is to get the engine up into the test stand. Years ago, this test stand was built for testing the Apollo Program S-II stage (the second stage of the Saturn V vehicle that was powered by five J-2 engines). Back then, they basically picked up the whole stage (from a canal barge, not a flatbed truck) high into the air and lowered it down from above into the stand. When it was converted to be an engine-only test stand for Space Shuttle Main Engine testing in the early 1970’s, propellant tanks were added on top of the stand. So you can no longer lower the test article in from way up above. Rather, you lift it up about four or five stories and then pull it in laterally. This is the “engine deck,” the level where the engine will be installed into the stand. In the pictures below you can see the operation of pulling the engine off the transport truck and up to the engine deck level of test stand A-2.

After the engine is lifted to the correct height, it is brought laterally into the stand and set down on the “porch.” That’s what the folks on the test stand call it: the porch. The other day somebody (obviously from out of town) mistakenly referred to it as the “veranda.” We’ll have none of that fancy talk around here! The thing onto which the engine is set is the Engine Vertical Installer (EVI). This is a hydraulic lift table that will be used to raise the engine into place when it is to be bolted to the test stand. So, here is the sequence: you lift the engine up to the engine deck level, you pull it into the stand and set the engine down on the EVI sitting on the porch, then you slide the EVI horizontally into the heart of the test stand (the EVI is on rails for this purpose), you then raise the engine into the test position, bolt it in place, and then you slide the EVI back out of the way. Ta-da! Now you’ve installed an engine for test!

In the pictures below you can see the technicians positioning the engine onto the EVI on the porch. In the bottom picture of the set, you can see in the background to the left test stand A-3 still under construction and, to the right, test stand A-1 where, early next year, J-2X powerpack testing will be conducted.

So, our little baby engine is all grown up and ready to see the great big world from high up in the test stand. The next phase of our development program is now begun: the testing phase. After the engine is installed and the test stand is readied for hot fire, J-2X development engine E10001 will be used to demonstrate basic operations such as start, mainstage, and shutdown, to verify main chamber combustion stability, and to provide initial validation of numerous systems-level simulations and models.

Okay, somebody go carefully poke the Datadogs because soon we’re going to have genuine, full-up rocket engine test data from J-2X. And, as a final note, I offer an extra special tip of the hat to all of the folks at SSC (NASA, Pratt & Whitney, and support contractors) for doing an amazing job in terms of engine assembly and test stand readiness preparations. Don’t ever think that your extraordinary efforts go unrecognized or unappreciated. Bravo!

J-2X Progress: Engine Assembly Complete

Just by chance, did you happen to see the title for this article? If not, please allow me the indulgence of repeating it…

Okay, I’m not ashamed. That felt good! We’ve all been working a long time to get to hoot and howl a bit about this. Wahoo! We are now officially into the next phase for J-2X development engine E10001.

Here, below on the left, was the engine sitting all cozy where it was assembled.

And on the right is the engine being lifted up and out of the assembly deck via an overhead crane. The techs then walked the engine out to the loading dock. There it was carefully loaded onto and mounted to a flatbed truck.

And next, our intrepid little will engine will brave the Mississippi heat on a gonzo road trip across the NASA Stennis Space Center to take up residence at the test stand. More on that coming soon!

J-2X Extra: Supplier Appreciation

Pssssssst. Come over here. Yes, you. Come on. Right here. Lean in real close because I’ve got a secret to share. A little closer. Are you ready? Okay, here it is: rocket engines are complex machines with lots and lots of pieces.

Well, maybe that’s not much of a secret. Maybe that’s just about as much of a secret as, say, “water is wet.” But what might not be known too well is how many different people get involved in developing and building a new rocket engine. Sure, the NASA office is located here at the Marshall Space Flight Center in northern Alabama, and the facility of our prime contractor for J-2X, Pratt & Whitney Rocketdyne is located in Los Angeles, California, and our engine assembly and test facility is at the NASA Stennis Space Center is southern Mississippi, but we engage more of the country than just those three key locations. The J-2X development effort has 362 different suppliers and vendors in 35 states and 4 in other countries.

Now, we here on the NASA side don’t chose the suppliers for this project. We sometimes get involved in okaying a supplier for various reasons pertaining to regulations (blah, blah, blah…snore…zzzzzzz…for a really good time, sit down and read the Federal Acquisition Regulation!), but it is primarily the job of our prime contractor to figure out what is needed and to hire appropriately. It’s just like having a general contractor if you were building a house. They have connections and know who best to call for the plumbing or the roof or the tiling in the bathroom.

So, we don’t pick ’em, and we certainly don’t endorse anyone over anyone else, but when a company steps forward and does a whiz-bang job for us – and therefore for our space exploration mission – I think that they deserve “atta-boy” recognition. Much earlier in this blog series, I included a picture taken at the facility of Cain Tubular Products in St. Charles, Illinois. They are a relatively small company that supplies our heat exchanger coils and they’ve done a whiz-bang job for us. We have other suppliers that are Fortune 100, multinational corporations like, for example, Honeywell International that provides the J-2X engine controller and several of the valve actuators. They too generally do a whiz-bang job for us.

So, here I’m going to shout out an “atta-boy” to another supplier…

Omni Electo Motive Inc. is located in Newfield, New York just outside Ithaca (beautiful country up there). To give you a general idea of what they do, I will quote their website: “Omni Electro Motive Inc. is one of the world’s premier independent manufacturers of custom manufactured gas turbine blades and vanes for jet engines and gas turbine industries.”

Well, okay, but it is not only jet engines and gas turbines that have turbine blades, so do rocket engines. As I’ve discussed before, the power of the engine comes from the power of the turbopumps. The turbine blades are small airfoils that convert the power of flowing hot, high pressure, high velocity gases into rotational power. Thus, they are a key component of the engine. Between the two turbopumps, the J-2X has over 300 turbine blades. Below is a picture of some turbine blades prior to assembly into the J-2X fuel turbopump. Each blade is fits snugly like a glove into a disk connected to the rotating shaft of the turbopump so that only the airfoil section is exposed.

These turbine blades not very big (easily fit in the palm of your hand), but they need to be exceedingly well made. They see extreme environments and undergo extreme loads during engine operation. In essence, they need to be as flawless as the finest jewels. That is why it takes a specialized supplier like Omni to do the job. However, more than just providing excellent products, Omni has engaged with the J-2X development team on the design side through multiple design iterations. The application of their extensive experience in this specialized field has been positively vital to our success.

Below is a picture of Omni Electromotive Inc. President, Frank Deridder (on the right), receiving a Supplier Appreciation Award from the Pratt & Whitney Rocketdyne J-2X Program Office.

Thank you very much guys for your dedication and for your commitment to excellence. “Atta-boy” and keep up the good work!

Front Row, From Left to Right: Holli Maneval, Adam Kellerson, Donald Koski, Mark Clauson.

Back Row From Left to Right: Ray Hornbrook, Matthew Oelkers, Brian Card, Jamie Brooks, John Case, Steven Vallimont

J-2X Progress: Test Stands Moving Towards Readiness

In the broadest sense, stepping back from the project, the J-2X development effort has three primary branches. First, of course, you have our prime contractor, Pratt & Whitney Rocketdyne (PWR) who is responsible for designing the engine and demonstrating that it meets the imposed requirements. Second, you have the team here at NASA responsible for management, technical oversight and insight, and, in a handful of specific cases, mainline work in support of PWR activities. And, third, you have the extensive efforts underway at the NASA Stennis Space Center (SSC) in southern Mississippi to provide a site for testing of the J-2X. If you scroll down a ways through previous articles you’ll see that I wrote an overview article about SSC and the test stands there. Here, for this article, I’m going to provide an update and show off some neato pictures of the ongoing work.

The first engine testing will take place on stand A2. In the picture below, technicians are using a locator tool to properly position the water spray ring to where it will need to be over the diffuser. The water spray ring is used to cool the top portions of the diffuser and is necessary since the first tests of the engine will not have any nozzle extension attached below the regeneratively-cooled nozzle. This means that the exhaust flow will not be entirely ‘turned’ and so it will impinge on the diffuser walls.

Next, after getting the spray ring close to the correct position using this tooling, the diffuser will be raised into position below the ring and a laser measurement system will be used to determine the exact location of the spray ring. At that point, the support arms will be installed so as to maintain that position.

In order to check out the extensive communications between the test control center, the test stand, and the engine itself, PWR shipped to SSC the first prototype engine controller. In the picture below what you see is the controller actually sitting on the test stand, on the same level where the engine will be during testing, talking back and forth with the stand. Of course, once the engine arrives, it will have its own controller mounted to the engine itself. This one is just being used for check-outs. Getting all such things checked out and running properly prior to installing the engine is crucial if you harbor any hopes of maintaining your schedule. This is a fine example of PWR and the crews at SSC working together towards a common goal.

When an engine is being tested, the area around it is pretty much cleared away. Almost anything close would be swept into the exhaust, or rattled apart, or melted from the heat in the plume. It’s truly a violent environment. But before and after the test, you need to be able to get your hands on the engine for a whole variety of reasons. For example: After a test, the engine needs to be dried. Remember that the combustion product for an oxygen-hydrogen engine is hot steam. When the engine cools after a test, that steam condenses and becomes water. In order to prepare for the next test, we have to dry out all that residual water and we do so by blowing heated gas, dry air or nitrogen, through the engine. So, we need access to the engine to hook up the hoses.

In the picture above are shown the lightweight, temporary platforms that have been created to allow for engine access. The engine will reside in the hole in the middle of the platforms. Prior to a test, these platforms are removed and after a test they are erected back in the position shown.

Okay, now we’re going to move over to the work being done on test stand A1. This is where we will first be testing the PowerPack Assembly (PPA). The PPA primarily consists of the turbomachinery and the gas-generator. It is essentially a special test bed for the propellant feed and turbine drive functions of the engine. Because the PPA does not have to feed a carefully balanced engine system and because we will be using special test equipment electro-mechanically activated, EMA, valves to control the PPA, we will have the freedom and ability to explore many more operational conditions for the turbomachinery than are possible during actual engine testing. This is a way to truly wring out the design with only a limited number of test articles. We will be calling the upcoming test article PPA2 since we had previously tested a PowerPack Assembly composed of legacy J-2S and XRS-2200 components back in 2007 and 2008. After PPA2 testing, test stand A1 will be converted back to a full engine test facility.

Just as we are using an engine controller to check out the communication systems, and just as we have special tooling for finding the right location for the spray ring on test stand A2, a special tool was developed by PWR to help the technicians at SSC properly position all of the plumbing that feeds into the engine. The tool is called a Master Interface Tool (MIT) and it is simply a bunch of fake interfaces all in the correct geometrical locations as though they were the real interfaces for an engine and PPA2. In the picture below, the MIT is the yellow item in the foreground. This portion of the MIT simulates the connections for all of the ancillary lines to the engine besides the main propellant flows.

Because the MIT properly emulates the engine, once all of the piping on the test stand side meets up with the tool, the technicians have much greater assurance that when an engine shows up, it will fit into the space provided. This is a much better approach than attempting to locate these lines in space with no solid reference point and it saves time since these lines can be installed now rather than waiting for the engine or the PPA2 to show up on the stand.

The MIT appears in the picture below as well. It is the yellow item on the bottom and here it is being used to position the installation of the liquid hydrogen and liquid oxygen feed lines. Thus, when we are actually up and running with an engine, it will hang right where the MIT is currently sitting.

The other yellow items in this picture, the beams that appear to extend up and into the rafters, are the structure that carries the thrust of the engine. These four beams will transmit a total of approximately a quarter of a million pounds-force of thrust into the thrust measurement system and into the test stand itself.

The last couple of pictures that I wanted to include here is intentionally less ‘glamorous’ than some of the previous ones showing where the engine will sit when tested or big pieces of tooling, etc. These pictures were taken in a couple of corners of the A1 test stand on the deck above where the engine will sit. These are the piping systems that will control and measure what on the vehicle would be the tank pressurization flows coming off the engine.

The intended point about these last two pictures is that the facilities necessary to properly test a rocket engine are quite involved and quite complex. The environments are vicious, the tolerances are tight, and everything that goes into or comes out of the engine needs to be controlled and measured. Indeed, the whole reason for doing engine testing is to gather data so as to better understand how well the design works.

Work continues. The formal Facility Readiness Reviews for these stands are currently scheduled for early March for test stand A2 and late April for test stand A1.

J-2X Extras: Rebuilding the Past

Several years ago, I was determined and ready to buy a new vehicle. I happened to be at my grandparents place at the time in upstate New York and my grandfather saw me perusing the local paper for dealerships making good deals. I told him that I was interested in getting a new pickup truck, something that I could use to go back and forth to grad school and carry all my stuff.

“Well, I’ll tell you what,” he said, “the best darn vehicle I ever had was a 1937 Ford Pickup. That thing just ran forever, it seems to me.” Then he winked, smiled, and added, “And, even better, I met your grandmother while I was driving that thing.”

So I went on down to the local Ford dealership and announced to the salesman wearing a plaid jacket and striped tie that I wanted to buy a pickup truck. My new best friend smiled a huge smile, shook my hand, and led me over to the part of the showroom dedicated to their latest line of beautiful F-150s.

“No, no,” I said, “I want to buy a 1937 pickup.”

“But we don’t sell used cars here, son, and certainly not classics like that.”

“I don’t want a used 1937 pickup,” I replied. “I want a new 1937 pickup.”

“There is no such thing,” he said, in an obvious state of confusion or maybe annoyance.

I scratched my head. “I don’t understand. I mean, you guys still have the drawings and such, right? And if you can build these big, shiny new things, then you can certainly go back and build something more simple, right? My granddad told me not to get suckered in. He said that I don’t need all these new-fangled bells and whistles.”

For the next hour, the salesman, named Pete by way (Pistol Pete, he chuckled to himself), tried to talk me into buying one of the current year models. He showed me everything, explaining with fast-talking expertise the dramatic advantages that his trucks had over the competition and even, he tossed in for me, far older models. But I was not totally convinced. Pistol Pete just shrugged and gave me his business card with a scribbled phone number for someone at their corporate headquarters who might be better able to help me. I left thinking that might have just lost the best friend I’d had for the last ninety minutes.

The next day, I called the corporate headquarters and tried to make clear what I wanted. I got bumped from department to department several times until I finally got someone named George seemingly willing to indulge me.

I told George what I wanted, but I also told him that I was impressed with what Pistol Pete the salesman had shown me. I said, “I’d really like to get that 1937 pickup with an automatic transmission, with overdrive, and cruise control. I would really like more speed and better handling. Better gas mileage too. Also, I’m thinking that I need more safety stuff, so I’d like that pickup to have air bags, modern crushable bumpers, and the latest auto glass. Plus, I’d like a bit more life and reliability, so building in that self-diagnostic system and computer would be good. And I read that some new body materials are less prone to corrosion, so build it out of new stuff.”

“So,” said George, who sounded perpetually half asleep when he spoke, “you want a 1937 pickup truck, with all modern features, built to all modern standards, with more performance, with better reliability, and with greater safety. Do I have that right?”

“Finally,” I said, “someone who understands! You’ve got it! That’s exactly what I want!”

“Right, then we will have to design you a new vehicle from scratch. That will take about two years of design effort, building a few prototypes, and then another couple of years of road testing and then certification from the federal highway authorities — which, by the way, will result in a bunch more changes unless you only want to drive it on Sundays and holidays like an antique car. Overall then I’m projecting that we’re talking, maybe, forty or fifty millions dollars as a starting point.”

“Huh? What are you talking about? That’s outrageous,” I yelled into the phone in dismay. “You built this thing 50 years ago, didn’t you? It didn’t cost that much then for goodness sake, even with inflation. Surely you’ve got the drawings just lying around somewhere, right?”

“No, actually we don’t,” said George in his tired monotone. “And even if we did and we had to build exactly a 1937 pickup, as it was built back then, it would be a project. To start, we would have to rebuild all of the tooling, recreate the materials we used back then, and reconstitute suppliers who have long since gone out of business. Add to that all of your new requirements and, well, you’ve got a whole new vehicle, right? So, basically, we’ll just have to start from scratch.”

I hung up the phone in an utter daze. Several weeks later, I bought a little Toyota pickup. I drove it for lots of years. I plan to someday tell my grandson that it was the greatest thing ever on four wheels and see where that leads…

One of the first questions that I got when I started this blog was why we didn’t just dust off the drawings of the old J-2 used for the Apollo Program and use that rather that launching into the J-2X development effort. Hopefully this little story provides a bit of insight by way of analogy. As we go along, I will tell you about the actual changes between the Apollo-era J-2 and the J-2X of today.

J-2X Progress: The J-2X Test Stands

Okay, so now you’ve got a great big rocket engine. What are you going to do with it? Well, fire it, of course. Make great big and noisy smoke and fire. There’s really not much that is more thrilling than an engine test…although, I guess, launches qualify (says the old engine guy reluctantly).

Engine Test at NASA Marshall Space Flight Center

But where are you going to do this? It’s not like you can do it in your garage. You’d blow away your entire neighborhood in the matter of a few seconds and the authorities tend to frown on such antics. Take a look (and listen) again at the video clip from the “What is a Rocket?” blog article to get an idea of what I’m talking about. Also, it’s not even like you can simply hire a company that specializes in testing stuff and there are many fine companies that do just that for all kinds of products big and small. No, rocket engine testing is an endeavor that requires its own dedicated facilities and infrastructure.

Over the past fifty years, NASA has developed a number of rocket engine test facilities, but by far the single largest and dedicated site is in southern Mississippi, Hancock County to be exact, today called the NASA Stennis Space Center (SSC). This facility is just about an hour from New Orleans. It is in a very secluded, woody bayou area far from any population centers. And that was the point when it was established. Given the size of the place needed to test rocket engines and rocket stages and given the noise that such testing makes, having no neighbors is basically a requirement.

Testing for the J-2X engine is currently planned in the “A-Complex” test area. That area is composed of three test stands. There are stands A1, A2, and A3 (no, it’s not an especially colorful naming scheme, I admit).

Stands A1 and A2 were designed to look like and function like the large test stand here at the NASA Marshall Space Flight Center. They were built in the 1960’s and were originally stage test facilities to accommodate testing of the S-II stage, the second stage of the Saturn V launch vehicle that took humans to the moon. The S-II stage was, of course, powered by the original J-2 rocket engine. Then in the early 1970’s, these two stands were converted into single-engine test stands to facilitate the development of the Space Shuttle Main Engine (SSME). Test stand A2 remained dedicated to SSME up until last year. Test stand A1 over the last thirty-five years was used primarily for SSME, but it was also used in the late 1990’s for the XRS-2200 linear aerospike engine development (which used a number of heritage J-2 and J-2S component designs) intended to support the X-33 vehicle.

Test Stand A2 Under Construction, Early 1960’s

S-II Stage being Hoisted into A2 in 1967 and the First SSME Test on A1 in May 1975

Test Stand A2 Today

Test stand A3 is a new facility currently being built specifically to accommodate development of the J-2X engine. It is unique in that it simulates the atmospheric pressures at high altitudes. Because the J-2X is being designed for maximum performance and for engine start at high altitudes, it is only within such a test facility as A3 that the complete configuration of the J-2X engine can be tested. The altitude simulation capability is produced by encapsulating the entire engine within a test chamber and using a system of steam ejectors to “suck down” the chamber using the Bernoulli effect familiar to students of fluid dynamics. Basically, what you have on A3 is a series of rocket engines, powered by liquid oxygen and alcohol, used to make a huge amount of high-velocity steam that creates a low-pressure environment into which the J-2X fires (itself also making a huge amount of steam). When A3 is up and running, the J-2X testing conducted there is going to be even more impressive than the usual engine tests.

Test Stand A3 Under Construction Today

The J-2X puts out approximately 300,000 pounds-force of thrust when fully configured and operating in space. As currently rigged, each of these three test stands can handle 600,000 pounds-force of thrust and, with some modifications, significantly more (the current thrust measurement systems being the limiting factor). Back when they were testing the S-II stages on A1 and A2, those stands were seeing nearly one million pounds-force of thrust with five J-2 engines firing simultaneously.

Within the last month, I had the opportunity to tour NASA SSC and see the progress of the work being done on these test stands to support the J-2X test campaign. Below are a series of photos with some accompanying commentary.

Above is a picture looking up and into the flame bucket on Stand A2. To give you an idea about dimensions, notice the person in the blue jacket and orange hardhat down on the right-hand wide. During an engine test, this entire area is deluged with water for the purposes of cooling and sound suppression. The flame bucket diverts the rocket exhaust from shooting downwards to shooting outwards and away from the stand. The long tube-like structure in the middle is a feature unique to Stand A2. It is a passive diffuser that creates simulated high-altitude conditions while the engine is running. The difference between this passive diffuser and the active diffuser on A3 is the fact that A3 can simulate higher altitudes and can do so even when the engine is not firing.

This is a shot taken near the top of stand A3. They have not yet built in the elevator so I know firsthand that the walk to the top is just about 23 flight of stairs, give or take a couple. I’ve marked stand A2 and also stand B1, which is currently used for RS-68 engine testing that supports the Delta IV launch vehicle. Stand A1 is off to the left, out of the frame of this picture. The low white building in the middle of the picture is the control room from where they conduct engine tests on A1 and A2. The control room for A3 will be in a different building.

Above is a picture of Jason Turpin (Liquid Engine Systems Branch, ER21, NASA MSFC) and Rick Ballard (Upper Stage Engine Element Systems Engineering and Integration Manager) standing on the Level 5 deck of stand A1 with the A3 construction site in the background. The water that you see behind them is part of a canal system that runs throughout the test area. On these canals they bring in barges filled with the propellants used for the testing. Back in the day, these canals were used to float in the assembled Saturn stages. This is not, however, necessary for engine testing since a single engine can be loaded onto a truck.

Overall, this tour of the facilities showed that NASA SSC is making tremendous progress in getting the test stands ready for the J-2X development test series campaign. In only a few months, we will be making smoke and fire (mostly steam!) and rumbling the acres of swampy woodlands that surround the site. I can hardly wait!