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J-2X Progress: Current Status, The End of 2012

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Once upon a time, not that long ago, people used to communicate by what were known as “letters.”  These were written documents.  Yes, actual hardcopy, paper items. And they were often transcribed by hand or, sometimes, generated on what was known as a “typewriter,” which was basically a manual, analog printer with no I/O port beyond direct keypad entry.  These “letters” were sent to their intended recipients using a small denomination currency with an adhesive backing that is recognized for exchange by only one quasi-governmental agency. 

I know that some of you may have doubts that people communicated with each other in primitive ways prior to email and text messages, but witness the cultural clues from the 1961 song illustrated above. 

It was always believed that the toughest letter to receive was the dreaded “Dear John” letter (as in, “Dear John, I’ve fallen in love with someone else…”).   However, I think t’at the hardest letter to write is the “it’s been awhile” letter.  This one starts, “Well, it’s been awhile since I’ve written.  Sorry.”  This blog article is just like one of those letters.  It’s been awhile since I’ve written one of these articles and I’m sorry about that.  I could give you a big long list of all the really, really serious stuff that I’ve been doing instead, but that’s just a bunch of feeble excuses so I’ll keep them to myself.  Instead, I’ll just get down to business and give you a status report on the J-2X development effort.

Engine #1 (E10001) Testing is Complete!
Over fourteen months and across the span of twenty-one tests, more than 2,700 seconds of engine run time was accumulated and recorded, including nearly 1,700 seconds of hot fire with an instrumented nozzle extension.  With this engine we achieved stable 100% power level operation by the fourth test and full mission duration by the eighth test.  While we don’t have any official statistics on the issue, most folks around here believe that we accomplished those milestones faster than has ever been done on a newly developed engine.  We learned how to calibrate the engine and the sensitivities that the engine has to different calibration settings, i.e., orifice sizes and valve positions.  We were able to estimate performance parameters for the full-configuration of the engine at vacuum conditions and the calculations suggest strongly that all requirements are met by this design and met with substantial margin.  This is significant considering that we’ve long considered our performance goals to be pretty aggressive.  Well, our little-engine-that-could showed us that it did just fine with those goals, thank you very much.

One of the truly unique and successful aspects of the E10001 testing was the testing of a nozzle extension.  This component is a key feature that allows J-2X performance to far exceed that of the J-2 engine from the Apollo Program era.  While it is true that we cannot test the full-length nozzle extension without a test stand that actively simulates altitude conditions, we did test a highly instrumented “stub” version that allowed us to characterize the thermal environments to which the nozzle is exposed during engine hot fire and it demonstrated the effectiveness and durability of the emissivity coating that was used.  This stub-nozzle configuration is actually the current baseline for the in-development Space Launch System vehicle upper stage.

Another key success for E10001 was the demonstration of both primary and secondary power levels with starts and shutdowns from each power level and with smooth in-run transitions back and forth between them.  That smoothness was thanks, in part, to demonstrating our understanding of the control of the engine.  From the very first test it was clear that we understood pretty well how to control the engine in terms of proper control orifices for the various operating conditions.  What we did not entirely understand — in other words the fine-tuning details — we successfully learned via trial-and-error throughout the E10001 test series.  All of this learning has been fed back into further anchoring our analytical tools and models so that we can move forward with J-2X development with a great deal of confidence.

Okay, so that’s a brief description of just some of the good stuff.  We had lots and lots of good stuff with the E10001 testing, far more than just that I’ve discussed here (see previous blog articles).  The somewhat unfortunate part was the way in which the E10001 test series came to an end.  On test A2J021, we had a disconnection between the intent for test and the detailed planning that led to the actual hardware configuration we ran for the test.  That disconnection led to an ill-fated situation.  Let me explain…

The J-2X gas generator has ports into which solid propellant igniters are installed.  These igniters are like really high-powered Estes® rocket motors that light off when supplied with a high-energy electrical pulse.  The flame from the igniter lights the fire of the hydrogen-oxygen mixture during the engine start sequence.  It’s essentially the kindling for the fire of mainstage operation.  The igniters perform this function at a very specific time during this sequence.  If you try to light the fire too early, then you may not have enough propellant available in a combustible mixture so you get a sputtering fire.  If you try to light too late, then you may have too much propellant built up such that rather than getting a good fire, you get an explosion instead.  But here’s a key fact: You have to plug them in or they don’t work.

Have you ever stuck bread in the toaster, pushed down the plunger, gone off to make the coffee, and come back only to find that your darn toaster is broken?  You curse a little because you’re already late for work and this is the last darn thing you need.  You would think that somebody somewhere could make a toaster that lasts more than six months or a year or whatever.  For goodness sake!  We put a man on the moon and yet we can’t … oh, wait … um … ooops, it’s not plugged in.  My bad.

In a nutshell, that’s what happened on test A2J021.  The electronic ignition system sent the necessary pulse, but because of the uniqueness of our testing configuration as opposed to our flight configuration the wires carrying the pulse weren’t hooked up to the little solid propellant igniters in the gas generator.  In the picture below you can see the external indication that something was not entirely good immediately after the test.  The internal damage was more extensive to both the gas generator and the fuel turbopump turbine.

Many years ago, I met an elderly engineer who was still on the job well into his 80’s because he loved his work.  His entire career had been dedicated to testing.  He’d actually been there, out in the desert, in the 1940’s testing our very earliest rockets as part of the Hermes Project.  One day, they had a mini disaster on the launch pad.  He told me that the rocket basically just blew up where it sat.  Boom and then a mess.  And, it was his job to assemble the test report.  Being a conscientious, ambitious, young engineer, he recorded the facts and offered a narrative abstract and extensive, annotated introduction that categorized the test as, well, a failure.  Not long after submitting his report, one of the senior German engineers in the camp came into his office, put the test report down on the desk, and said that the tone of the report was entirely wrong.  He said, “Every test report should begin with: ‘This test was a success because…'”  The purpose of testing is to gather data and learn.  If you learn something, then your test was, by definition, a success on some level.  I’ve tried very hard to remember this very important bit of wisdom.

So, A2J021 was a success because we learned that we had some deficiencies in our pre-test checkout procedures.  It was a success because it was an extraordinary stress test on the gas generator system.  No, it didn’t recover and function properly, but neither did the engine come apart.  While that might seem like a minor detail, when you’re hundred miles from the surface of the earth, you would much rather have a situation where an abort is possible than a failure that could result in collateral vehicle damage and make safe abort impossible.  We have a stout design.  Good.  Also, this test failure was due to a unique ground test configuration.  In flight, it’s not really plausible just because we would never fly in this configuration.

So, E10001 completed its test program with a bang.  Kinda, sorta literally.  But it was nearly the end of its design life anyway, so we didn’t lose too many test opportunities, and, as I said, even with test A2J021 the way it happened we learned a great deal.  Overall, the E10001 test series was an outrageous success.  Rocketdyne, the J-2X contractor, ought to be darn proud and so should the outstanding assembly and test crews at the NASA Stennis Space Center and our data analysts here at the NASA Marshall Space Flight Center.  Bravo guys!  Go J-2X!

Power-Pack Assembly 2 (PPA-2) Testing is Complete!
Over ten months and across the span of thirteen tests, nearly 6,200 seconds of engine run time was accumulated and recorded on the J-2X Power Pack Assembly 2.  That’s over 100 minutes of hot fire.  Three of the tests were over 20 minutes long (plus one that clocked in at 19 minutes) and these represent the longest tests ever conducted at the NASA Stennis Space Center A-complex.  But more than just length, it was the extraordinary complexity of the test profiles that truly sets the PPA-2 testing apart.

Because PPA-2 was not a full engine with the constraints imposed by the need to feed a stable main combustion chamber, and because we used electro-mechanical actuators on the engine-side valves and hydraulic actuators on the facility side valves, we could push the PPA-2 turbomachinery across broad ranges of operating conditions.  These ranges represented extremes in boundary conditions and extremes in engine conditions and performance.  On several occasions we intentionally searched out conditions that would result in a test cut just so that we could better understand our margins.  As the saying goes: It’s only when you go too far do you truly learn just how far you can go.  We successfully (and safely) applied that adage several times.  In short, we gathered enough information to keep the turbomachinery and rotordynamics folks blissfully buried in data for months and months to come. 

On an interesting and instructive side note, the PPA-2 testing also showed us that we needed to redesign a seal internal to the hydrogen turbopump.  In the oxygen turbopump, you have an actively purged seal between the turbine side and the pump side.  After all, during operation you have hydrogen-rich hot gas pushing through the turbine side and liquid oxygen going through the pump side.  You obviously don’t want them to mix or the result could be catastrophic.  That’s why we have a purged seal.  But for the hydrogen turbopump you don’t have such an issue.  During operation, at worst should the two sides mix you could get some leakage of hydrogen from the pump side into the turbine side that is already hydrogen rich.  In order to maintain machine efficiency, you don’t want too much leakage, but a little is not catastrophic (and can be used constructively to cool the bearings).  What could be dangerous at the vehicle level, however, is if you have too much hydrogen floating around prior to liftoff.  This is especially true for an upper-stage engine like J-2X that’s typically sitting within an enclosed space until stage separation during the mission.  You could have the engine sitting on the pad for hours chilling down and filling the cryogenic systems and you don’t want gobs and gobs of hydrogen leaking through the turbopump since any leakage ends up within the closed vehicle compartment housing the engine.  That’s just asking for an explosion and a bad day.

To avoid this, within the J-2X hydrogen turbopump we have what is called a lift-off seal.  And, as the name applies, it’s a seal that actively lifts off when we’re ready to run the engine.  When the engine is just sitting there chilling down, not running, with liquid hydrogen filling the pump end of the hydrogen turbopump, the seal is, well, sealed.  Then, when we’re ready to go, it unseals and allows the turbopump to operate nominally.

During the PPA-2 test series we found that we formed a small material failure within the actuation pieces for our lift-off seal.  Then, upon analysis of the test data and a reassessment of the design, we figured out what was most likely the cause and Rocketdyne proposed a redesign to mitigate the issue.  Again, going back to that important piece of wisdom: This testing was a success because, in part, we learned that we needed a slight redesign of the lift-off seal.  That’s the whole purpose of development testing!  Everything always looks great when it’s just in blueprints.  It’s not until you hit the test stand do you truly learn what’s good and what need to be reconsidered.  In the end, this sort of rigor and perseverance is what gives you a final product that you feel good about putting in a vehicle carrying humans in space.  And that, truly, is what it’s all about.

As with E10001, the PPA-2 test series was simply an outrageous success.  Rocketdyne should be proud and so should the outstanding assembly and test crews at the NASA Stennis Space Center and the data analysts at the NASA Marshall Space Flight Center.  Bravo guys!  Go J-2X!

Engine #2 (E10002) Assembly is Underway
Our next star on the horizon is J-2X development Engine 10002.  It is being assembled right now, as I’m typing this article.  It is slated for assembly completion in January 2013 and it will be making lots of noise and very hot steam in the test stand soon after that.  While our current plans are to first test E10002 in test stand A2, we will later be moving it to test stand A1.  This, then, will be the first engine then to see both test stands.  The more important reason for the A1 testing, however, is because that will give us the opportunity to hook up some big hydraulic actuators and gimbal the engine, i.e., make it rock and tilt as though it were being used to steer a vehicle.  Now that will be some exciting video to post to the blog!  I can’t wait.

Happy New Year!
So, this has been my “it’s been awhile” letter.  Hopefully this will bring everyone up to speed with where we stand with J-2X development.  In my next article, I will share with you some of what’s been keeping me from my J-2X article writing over the last several months.  And, hopefully, it won’t be several months in the making.  So, farewell for now and Happy New Year!  On to 2013 and another great year full of J-2X successes.  Go J-2X!

Inside The J-2X Doghouse: A2J006 &Turbopump Thrust Balance

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Okay, before I even get to the subject of thrust balance, I want to report that J-2X development engine E10001 got back into the stand and that the next test, A2J006, was conducted.  The test went the full planned duration of 40 seconds and the issues that caused us to remove the engine after the previous test all appear to be fixed.  In other words, it was a complete success.  Here’s a video for your viewing pleasure:




Now, speaking of issues on E10001 that appear to be resolved, I want to talk about turbopump thrust balance.  While I hadn’t previously mentioned it, the data from the first several tests showed that there was a thrust balance issue with the oxidizer turbopump (OTP).  So, that naturally leads to the question:  What is “thrust balance?”


Here is a crude drawing of a turbopump for this discussion (And, please, save your cards and letters telling me that I am a terrible artist.  I will already catch plenty of grief from the turbo guys over this drawing.).  The arrows are intended to illustrate fluid flows.



I’ve drawn this in three colors because a turbopump can be thought of as having three fundamental elements.  The first element, the one in blue, is the part that spins.  This is the rotor onto which is attached the pumping stuff (i.e., the inducer and the impeller) on the pump side and the turbine stuff (i.e., the disks and blades) on the turbine side.


The second element, shown in green, is the part that doesn’t spin.  This is the housing.  It is the shell within which the rotor spins.

The third element, shown in red, is the bearings. 


Whenever you’ve got one thing spinning and another thing stationary, you’ve got to have some way of communicating between the two pieces.  Maybe the rotor just spins and slides around in some kind of restraint holding it in place.  Well that might work except that you can’t put grease into a cryogenic oxygen environment and, should too much heat build-up due to friction, then you’ve got a very combustible situation.  Mix heat with a pure oxygen environment and anything and everything will burn, including metal. 


What we do instead is typically use ball bearings between the rotor and the housing.  In some other pumps we use roller bearings that look like little cylinders rather than little balls, and there are other solutions as well.  These bearings do two things, they allow the rotor to spin and they hold the rotor in place.  So they need to be loose enough to spin yet tight enough to maintain control of a heavy hunk of metal spinning at over 10,000 rpm.  How much force the bearing put on the rotor to maintain control and, conversely, how much the rotor puts back on the bearings is called the bearing load. 

When you are designing a turbopump, you design it so that the bearings have a specific load, and that means more than just a value, it also means a direction as shown in the sketch above.  You design the whole bearing package assuming that you know the magnitude and direction of the forces loaded through the package.  This then allows you to do some calculations that tell you, “Yep, I’ve got the rotor properly and sufficiently controlled.”  Those calculations are part of what is often referred to as rotordynamics (and, by the way, NASA MSFC has some of the world’s best experts in that area).


Question: How do you get different bearing loads in a turbopump?  Answer: Pressures.


Here is a nifty little fact: Pressure is all around us.  We don’t feel the atmospheric pressure of 14.7 pounds-force over every square inch of your body because, well, it’s always been there.  That’s the environment within which we’ve evolved.  Now, go to the bottom of the ocean and you’ll find a whole other pressure environment, one that would crush our delicate bodies into mess.  The basic principle to remember is this: Pressure applied over an area equals force.


Within a turbopump, you are explicitly manipulating pressure.  That’s the whole purpose of a pump: to move fluid through the use of pressure.  So, in the pump end you have a low pressure coming in at the inlet and a very high pressure at the outlet.  On the turbine end, it’s the opposite since on that end you’re extracting energy (and therefore pressure) from the fluid.  So, on the turbine end you have high pressure at the inlet and lower pressure at the outlet.  Thus, throughout the turbopump, you’ve got pressures of all sorts and those pressures are pushing on the different pieces of the rotor.  This means that you’ve got all kinds of forces pushing on the rotor.  Some of the forces push the rotor towards the turbine end.  Some of the forces push the rotor towards the pump end.  Getting the right balance of forces is called your thrust balance.




So, what’s the “right” thrust balance?  It is the one to which you’ve designed your bearings.  You design your bearings to have a certain load and a big part of that load is determines by the thrust balance on the rotor.  So, if your thrust balance is off, i.e., not what you intended, then your bearing loads are off and you’re therefore not controlling the rotor the way that you wanted.  In the worst of circumstances, an out-of-control rotor represents a catastrophic situation.  In less-than-worst circumstances, operating with a thrust balance significantly different than the design intent could lead to unexpected wear on components and therefore limited operational life. 


The next question is this: How do you create the thrust balance that you want and need to accomplish all this? 


That’s a matter of designing the internal guts of the turbopump and analytically modeling all of the internal flows within these guts.  In addition to the big flows coming into and out of the pump and turbine, you’ve got internal flows around seals, between pump or turbine stage, and through the bearings (as coolant).  When operating, the whole turbopump is full of fluid.  And, everywhere you have fluid, you have a pressure; and everywhere you have pressure applied to an area, you have a force.  So you calculate pressure drops through small passages or through seals and figure out a whole detailed map of different pressures and forces throughout the whole unit and you can understand your thrust balance.  And then, as necessary, you manipulate your clearances and seals and passages designs until you achieve the thrust balance you need.




Getting back to the E10001 OTP, what appears to have been the issue was that we had some seals that were too tight.  The tight seals overly restricted internal flows and, basically, messed up the intended force balance on the rotor.  This could be seen in the data collected from the testing.  Remember when I said several articles ago that this engine is instrumented to the max so that we can learn all about how it is working.  Here is a case where special instrumentation identified an issue.  The interesting part is that these seals were kinda sorta fine in terms of design but the processing of the material of which they are made — it feels like hard plastic — was not quite refined enough so that when subjected to operational conditions it changes dimensions and actually tightened up. 


Prior to test A2J006, while we had the engine out of the stand, our contractor Pratt & Whitney Rocketdyne was able to partially disassemble the engine and the OTP just enough to change out the seals in question and then get the whole thing buttoned up and ready for test in record time.  They truly did some excellent work here.  And the success of test A2J006 is the proof!


J-2X Extra: Supplier Appreciation

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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: Turbomachinery — The Rotating Components

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It was once pointed out to me that most of a rocket engine really isn’t a whole lot more than a jumbled bunch of specialized plumbing.  Notable exceptions to that general rule are the engine controller — the brain of the engine — and the rotating components, i.e., the turbomachinery.  Of course, the person who was telling me this was a turbomachinery person, which means that I cannot entirely concede the point lest I yield my traditional posture of giving them a hard time.  But there is no denying that rocket engine turbopumps are truly remarkable pieces of machinery.

What is a rocket engine turbopump?  Typically, and this is true for J-2X, a turbopump consists of two parts: a turbine and a pump (hence the name).  Pump portion is what draws in the propellants into the engine the pushes that fluid through all of the “plumbing” that leads, ultimately, to its fiery, thrust-generating expulsion.  The turbine portion is what provides power to drive the pump.  The turbine converts the power of hot gases into the power of rotational machinery.  The pump converts the power of rotational machinery into fluid power otherwise known as pressure (thousands of pounds-force per square inch) within the propellant being pumped.  For J-2X, there are two turbopumps: one for pumping liquid hydrogen (fuel) and one for pumping liquid oxygen (oxidizer, or often called “LOX”). 

Soon, I will be writing an article for this blog that further explains the system-level workings of a gas-generator-cycle rocket engine like J-2X.  So, stay tuned.

Recently, the Pratt & Whitney Rocketdyne (PWR) / NASA turbomachinery team has made significant progress toward completing the final assemblies of the hydrogen and oxygen turbopumps for the first J-2X development engine (E10001).  The first two images show two major milestones for the liquid oxygen turbopump.  In the first picture, the turbine-end manifold (top of the photo) is shown being mated to the pump-end volute that is secured in the build dolly.

J-2X Liquid Oxygen Turbopump after Successful Turbine Manifold Installation

The second picture shows that the oxygen turbopump has now been flipped over with the pump end now near the top of the image and the turbine manifold below.  It is sitting in an oven where it underwent a drying operation after successful insertion of the first-stage turbine disk and the turbopump shaft.

J-2X Liquid Oxygen Turbopump Following First Stage Turbine Disk and Shaft Installation

The hydrogen turbopump has also made good progress by completing all pump-end assembly operations and the turbine manifold installation.  The first picture of the fuel turbopump below was taken after the successful assembly of the impeller into the bearing support, and subsequently that bearing support assembly being installed into the pump end volute, which has been chilled in cryogenic liquid nitrogen.  The nitrogen was used to create the proper fit for the volute and the bearing support to prevent hydrogen leakage under engine operating conditions.

J-2X Liquid Hydrogen Turbopump After Successful Mating of Volute and Turbine Bearing Support

The process of (1) chilling one metal piece so cold that it shrinks, (2) heating another metal piece so warm that it expands, and (3) then fitting the two pieces together in those states is a process used throughout engine assembly on many different components.  It is a means for accomplishing an “interference fit” (also called a “compression fit” or a “press fit”), which means that the two parts, machined to their appropriate tight tolerances, would otherwise not quite fit together — almost but not quite.  At room temperature, the pieces would interfere with each other if you tried to push them together.  The chill/heat process during assembly allows them to fit together very, very tightly.

The second fuel turbopump picture below shows the successful installation of the turbine manifold onto the turbine bearing support representing a major milestone in the assembly process.

J-2X Liquid Hydrogen Turbopump Turbine Manifold Installed Onto Bearing Support

In the beginning of this article, I told you that rocket engine turbopumps are remarkable pieces of machinery.  Yet, what I have shown you in the pictures are mostly images of shiny-metal external pieces, big hulking manifolds and volutes.  For reasons largely having to do with export control considerations (Rule #1: blog author does not go to prison!), I cannot show you pictures or detailed schematics of the inner workings.  I can describe them by saying that on the pump side you have an inducer, which looks like a fluid screw, and that feeds an impeller for a typical centrifugal pump.  On the turbine side, I can tell you that there are two rotating disks of turbine blades and, effectively, two rows of stationary blades called stators or nozzles.  And in between the pump ends and the turbine ends are a series of seals that separate the two ends.  Ideally, the only contact between the pump and turbine ends would be the mechanical power of the rotating shaft. 

To give you a better appreciation of the “remarkable” aspects of these units, let’s consider these machines in terms of their output.  In terms of horsepower, the table below compares various machines with which you are likely familiar.  At only 30 inches long and 20 inches in diameter, the J-2X hydrogen turbopump produces an incredible 16,000 horsepower.  This power level is equivalent to more than 120 automobiles, or 90 light aircraft, or even 5 diesel-electric locomotives.  In terms of energy generated in a small package, the J-2X fuel pump provides almost as much power as a large aircraft engine on the Boeing 747.

The two turbopumps for the first J-2X development engine are currently on track to complete assembly in December.  These units will then be boxed up, shipped to NASA Stennis Space Center, and await engine assembly.  So, the first development engine coming soon!  And then, it’s on to testing!

Note that thanks are due to Jeff Thornburg, Upper Stage Engine Element Deputy Turbomachinery Subsystem Manager, for providing the largest portion of the technical updates and pictures that informed this article.