Editor’s note: This is the second in a two-part series on the chemical reactions at the heart of rocket propulsion. Last week, we talked about the liquid engines of the SLS core stage , this week we’ll talk about the boosters.
By Beverly Perry
To give SLS extra power to get it off the ground, twin five-segment rocket boosters, built by Orbital ATK, tower more than 17 stories tall, burn six tons of solid propellant each second and help SLS break free from the clutches of Earth’s gravity.
Solid rocket fuel is the original rocket fuel, dating back to the early fireworks developed by the Chinese centuries ago. For the SLS boosters, aluminum powder serves as the fuel and a mineral salt, ammonium perchlorate, is the oxidizer.
The powerful aluminum-ammonium perchlorate reaction fuels the twin SLS solid rocket boosters.
Aluminum is the most abundant metal on Earth. It’s also highly reactive. Aluminum is so reactive, in fact, that it’s not found naturally in its pure form but only in combination with other minerals. It’s this ability to readily combine with other metals that makes aluminum so useful. Every day, we use products made of aluminum alloys, or mixes with other metals, for things like beverage containers, covering leftovers, or iPhones. Amazingly, it’s this same stuff that fuels solid rocket boosters.
Ammonium perchlorate, the salt of perchloric acid and ammonia, is a powerful oxidizer (read: majorly explosive). In the boosters, the aluminum powder and ammonium perchlorate are held together by a binder, polybutadiene acrylonitrile, or PBAN. The mixture, with the consistency of a rubber eraser, is then packed into a steel case.
This is what the inside of the empty booster case looked like after the first qualification motor test in March 2015. Preparations are already well underway for the second qualification test this summer.
When it burns, oxygen from the ammonium perchlorate combines with aluminum to produce aluminum oxide, aluminum chloride, water vapor and nitrogen gas – and lots of energy.
This reaction heats the inside of the solid rocket boosters to more than 5,000 degrees Fahrenheit, causing the water vapor and nitrogen to rapidly expand. Just like in the liquid engines, the nozzle funnels the expanding gases outward, creating thrust and lifting the rocket from the launch pad.
Compared to liquid engines, solid motors have a lower specific impulse – the measure rocket fuel efficiency that describes thrust per amount of fuel burned. However, the propellant is dense and burns quite quickly, generating a whole lot of thrust in a short time. And once they’ve burned their propellant and helped propel SLS into space, the boosters are discarded, lightening the load for the rest of the spaceflight.
So that’s it really. Make water and shoot off an enormous firecracker and you’ve got: Rocket Chemistry. On this scale though, you can’t try this at home. Watch the real show when SLS launches in 2018.
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If you guessed that water and aluminum make SLS fly, give yourself a gold star!
Chemistry is at the heart of making rockets fly. Rocket propulsion follows Newton’s Third Law, which states that for every action there is an equal and opposite reaction. To get a rocket off the launch pad, create a chemical reaction that shoots gas and particles out one end of the rocket and the rocket will go the other way.
What kind of chemical reaction gets hot gases shooting out of the business end of a rocket with enough velocity to unshackle it from Earth’s gravity? Combustion.
Whether it’s your personal vehicle or a behemoth launch vehicle like SLS, the basics are the same. Combustion (burning something) releases energy, which makes things go. Start with fuel (something to burn) and an oxidizer (something to make it burn) and now you’ve got propellant. Give it a spark and energy is released, along with some byproducts.
For SLS to fly, combustion takes place in two primary areas: the main engines (four Aerojet Rocketdyne RS-25s) and the twin solid rocket boosters (built by Orbital ATK) that provide more than 75 percent of thrust at liftoff. Combustion powers both propulsion systems, but the fuels and oxidizers are different.
Steam clouds, the product of the SLS main engines’ hydrogen-oxygen reaction, pour from an RS-25 engine during testing at NASA’s Stennis Space Center.
The RS-25 main engines are called “liquid engines” because the fuel is liquid hydrogen (LH2). Liquid oxygen (LOX) serves as the oxidizer. The boosters, on the other hand, use aluminum as fuel with ammonium perchlorate as the oxidizer, mixed with a binder that creates one homogenous solid propellant.
Making water makes SLS fly
Hydrogen, the fuel for the main engines, is the lightest element and normally exists as a gas. Gases – especially lightweight hydrogen – are low-density, which means a little of it takes up a lot of space. To have enough to power a large combustion reaction would require an incredibly large tank to hold it – the opposite of what’s needed for an aerodynamically designed launch vehicle.
To get around this problem, turn the hydrogen gas into a liquid, which is denser than a gas. This means cooling the hydrogen to a temperature of ‑423 degrees Fahrenheit (‑253 degrees Celsius). Seriously cold.
Although it’s denser than hydrogen, oxygen also needs to be compressed into a liquid to fit in a smaller, lighter tank. To transform oxygen into its liquid state, it is cooled to a temperature of ‑297 degrees Fahrenheit (‑183 degrees Celsius). While that’s balmy compared to LH2, both propellant ingredients need special handling at these temperatures. What’s more, the cryogenic LH2 and LOX evaporate quickly at ambient pressure and temperature, meaning the rocket can’t be loaded with propellant until a few hours before launch.
Once in the tanks and with the launch countdown nearing zero, the LH2 and LOX are pumped into the combustion chamber of each engine. When the propellant is ignited, the hydrogen reacts explosively with oxygen to form: water! Elementary!
2H2 + O2= 2H2O + Energy
This “green” reaction releases massive amounts of energy along with superheated water (steam). The hydrogen-oxygen reaction generates tremendous heat, causing the water vapor to expand and exit the engine nozzles at speeds of 10,000 miles per hour! All that fast-moving steam creates the thrust that propels the rocket from Earth.
It’s all about impulse
But it’s not just the environmentally friendly water reaction that makes cryogenic LH2 a fantastic rocket fuel. It’s all about impulse – specific impulse. This measure of the efficiency of rocket fuel describes the amount of thrust per amount of fuel burned. The higher the specific impulse, the more “push off the pad” you get per each pound of fuel.
The LH2-LOX propellant has the highest specific impulse of any commonly used rocket fuel, and the incredibly efficient RS-25 engine gets great gas mileage out of an already efficient fuel.
But even though LH2 has the highest specific impulse, because of its low density, carrying enough LH2 to fuel the reaction needed to leave Earth’s surface would require a tank too big, too heavy and with too much insulation protecting the cryogenic propellant to be practical.
To get around that, designers gave SLS a boost.
Next time: How the solid rocket boosters use aluminum – the same stuff you use to cover your leftovers – to provide enough thrust to get SLS off the ground.
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Earlier this month, another successful test firing of a Space Launch System (SLS) RS-25 engine was conducted at Stennis Space Center in Mississippi. Engine testing is a vital part of making sure SLS is ready for its first flight. How do the engines handle the higher thrust level they’ll need to produce for an SLS launch? Is the new engine controller computer ready for the task of a dynamic SLS launch? What happens when if you increase the pressure of the propellant flowing into the engine? SLS will produce more thrust at launch than any rocket NASA’s ever flown, and the power and stresses involved put a lot of demands on the engines. Testing gives us confidence that the upgrades we’re making to the engines have prepared them to meet those demands.
If you read about the test – and you are following us on Twitter, right? – you probably heard that the engine being used in this test was the first “flight” engine, both in the sense that it is an engine that has flown before, and is an engine that is already scheduled for flight on SLS. You may not have known that within the SLS program, each of the RS-25 engines for our first four flights is a distinct individual, with its own designation and history. Here are five other things you may not have known about the engine NASA and RS-25 prime contractor Aerojet Rocketdyne tested this month, engine 2059.
Engine 2059 roars to life during testing at Stennis Space Center.
1. Engine 2059 Is a “Hubble Hugger” – In 2009, the space shuttle made its final servicing mission to the Hubble Space Telescope, STS-125. Spaceflight fans excited by the mission called themselves “Hubble Huggers,” including STS-125 crew member John Grunsfeld, today the head of NASA’s Science Mission Directorate. Along with two other engines, 2059 powered space shuttle Atlantis into orbit for the successful Hubble servicing mission. In addition to its Hubble flight, engine 2059 also made four visits to the International Space Station, including the STS-130 mission that delivered the cupola from which station crew members can observe Earth below them.
The engine farthest to the left in this picture of the launch of the last Hubble servicing mission? That’s 2059. (Click for a larger version.)
2. The Last Shall Be First, and the Second-to-Last Shall Be Second-To-First – The first flight of SLS will include an engine that flew on STS-135, the final flight of the space shuttle, in 2011. So if the first flight of SLS includes an engine that flew on the last flight of shuttle, it only makes sense that on the second flight of SLS, there will be an engine that flew on the second-to-last flight of shuttle, right? Engine 2059 last flew on STS-134, the penultimate shuttle flight, in May 2011, and will next fly on SLS Exploration Mission-2.
The test of engine 2059 at Stennis Space Center on March 10.
3. Engine 2059 Is Reaching for New Heights – As an engine that flew on a Hubble servicing mission, engine 2059 has already been higher than the average flight of an RS-25. Hubble orbits Earth at an altitude of about 350 miles, more than 100 miles higher than the average orbit of the International Space Station. But on its next flight, 2059 will fly almost three times higher than that – the EM-2 core stage and engines will reach a peak altitude of almost 1,000 miles!
Click to see larger version.
4. Sometimes the Engine Tests the Test Stand – The test of engine 2059 gave the SLS program valuable information about the engine, but it also provided unique information about the test stand. Because 2059 is a flown engine, we have data about its past testing performance. Prior to the first SLS RS-25 engine test series last year, the A1 test stand at Stennis had gone through modifications. Comparing the data from 2059’s previous testing with the test this month provides calibration data for the test stand.
Attendees of a NASA Social visiting Stennis Space Center being photobombed by engine 2059.
5. You – Yes, You – Can Meet Awesome SLS Hardware Like Engine 2059 – In 2014, participants in a NASA Social at Stennis Space Center and Michoud Assembly Facility, outside of New Orleans, got to tour the engine facility at Stennis, and had the opportunity to have their picture made with one of the engines – none other than 2059. NASA Social participants have seen other SLS hardware, toured the booster fabrication facility at Kennedy Space Center in Florida, and watched an RS-25 engine test at Stennis and a solid rocket booster test at Orbital ATK in Utah. Watch for your next opportunity to be part of a NASA Social here.
This week’s Rocketology post is by the newest member of the SLS communications team, Beverly Perry.
When NASA’s Space Launch System (SLS) first flies, it will slice through Earth’s atmosphere, unshackling itself from gravity, and soar toward the heavens in an amazing display of shock and awe. To meet the engineering challenges such an incredible endeavor presents, NASA’s Marshall Space Flight Center draws upon a vast and diverse array of engineering talent, expertise and enthusiasm that spans multiple disciplines and, in some cases, a generation. Or two.
Kathryn Crowe is a twenty-something aerospace engineer who tweets from her smartphone and calls herself a “purveyor of the future.” Hugh Brady, on the other hand, began his career at Marshall during the days of punch cards and gargantuan room-sized IBM mainframes with an entire 16 kilobytes (!) of memory.
While they’ve had very different experiences, Kathryn Crowe and Hugh Brady share a common excitement for their work on SLS.
But if you think these two don’t have much common ground on which to build a strong working foundation, well, think again. Although the two aerospace engineers may be separated by a couple generations, they speak of each other with mutual admiration, respect and enthusiasm. And like any relationship built on a solid foundation, there’s room for fun, too.
Even though Brady’s career spans 50-plus years at NASA, he’s anything but jaded, to hear Crowe tell it. “Hugh still seems to keep that original sense of excitement. I figure if he thinks I’m doing okay, then I must be doing okay since he’s seen almost our entire history as an agency. It’s nice to have him to help keep me straight,” says Crowe, who recently received NASA’s Space Flight Awareness Trailblazer Award, which recognizes those in the early stages of their career who demonstrate creative, innovative thinking in support of human spaceflight. “And, he always tries to bring a sense of humor to everything he does.”
“I’ve enjoyed being mentored by Kathryn,” jokes the seventy-something Brady, who admits to failing retirement (twice, so far) because he loves the space program and can’t stay away. (Also, he said, because he doesn’t care for television. But mostly it’s because he loves space exploration and working with young, talented engineers.)
Crowe and Brady have worked together evaluating design options and deciding on solutions to make the second configuration of SLS as flexible and adaptable as possible. This upgraded configuration – known as Block 1B – adds a more-powerful upper stage and will stand taller than the Saturn V. It could fly as early as the second launch of SLS, which will be the first crewed mission to venture into lunar orbit since Apollo. Block 1B also presents the opportunity to fly a co-manifested payload, or additional large payload in addition to the Orion crew capsule.
The addition of an Exploration Upper Stage to SLS will make the rocket more powerful and open up new mission possibilities.
For Crowe, a self-described “shuttle baby,” working on a future configuration of SLS means the chance to look at the big picture. “I like to have a global view on things. For this particular rocket, we’ve made it as flexible as we can. We can complete missions that we don’t even know the requirements for yet!”
For Brady, “Things have a tendency to repeat.” While technology and solutions continue to improve, some of the challenges of spaceflight will always remain the same. When it comes to wrestling with the challenges of a co-manifested payload, Brady draws on his experience, but focuses on solutions that are tailored for SLS. It’s bringing lessons from the past into the present in order to find the best solution for future missions. “It’s drawing on what we’ve learned from the past but not necessarily repeating the past. We want the best solution for this vehicle,” he emphasizes.
Crowe says the experience and knowledge Brady brought to the table made all the difference when studying options for the SLS vehicle. “Hugh would say, ‘I think we worked on this particular technical problem when we were initially flying.’ He could draw parallels so we didn’t reinvent the wheel,” Crowe says. Since then, Brady has become something of a mentor to Crowe and other younger team members.
“When you put that kind of technical information on the table it gives people better information – information that’s based on prior experience,” Brady says. “We may not pick the same solution, because technology changes over time, but we will have more and better information to use when making decisions.”
“I think that having that kind of precedent to build upon it really is a beautiful thing,” Crowe says.
For his part, Brady says he feels a “comfort” level in passing the United States’ launch vehicle capabilities on to the next generation of engineers and other supporting personnel. “One of the things I find very exciting is to look around and see the young talent around the center with their energy and enthusiasm. I feel good thinking about when I do hang it up – again – that they will carry on and even do more than we did,” he says.
When you ask Crowe if humans will get to Mars, she says, “For sure I think within my lifetime I will see humans on Mars. I think more than ever right now is the right time to return to human spaceflight. We have the right skills and expertise. And when we successfully complete our mission and show that sort of hope to people again, that’s going to be equally as important as technological benefits.”
“That’s the objective,” Brady says. “I can’t wait until we fly again. It’s a tremendous feeling! It’s exhilarating! It’s time.”
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On one end of the technology spectrum, you have rocket science, mastering the laws of physics to allow human beings to break the chains of gravity and sail through the void of space.
On the other end, you have the earliest humans, first learning to use the world around them in innovative ways to do things they previously couldn’t.
What do these two extremes have in common? Making fire. Just like the secret to learning to cook food was mastering the creation of flames, creating fire is also the secret to leaving the planet.
We just use a much bigger fire.
Solid rocket motors and liquid-fuel engines will work together to propel the first SLS into space.
If you’ve watched the first video in our No Small Steps series you’ve learned why going to Mars is a very big challenge, and why meeting that challenge requires a very big rocket. In the second installment we talked about how NASA’s Space Launch System (SLS) builds on the foundation of the Saturn V and the space shuttle, and then uses that foundation to create a rocket that will accomplish things neither of them could.
Now, the third No Small Steps video takes a step further by looking at the basics of the monumental energy that makes the rocket go up. If you’ve been following this Rocketology blog and the No Small Steps videos, you’re aware that the initial configuration of SLS uses two different means of powering itself during launch – solid rocket boosters and liquid-fuel engines.
But why? What’s the difference between the two, and what role does each play during launch? Well, we’re glad you asked, because those are exactly the questions we answer in our latest video.
With more SLS engine and booster tests coming in the next few months, this video is a great way to get “fired up” about our next steps toward launch.
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During his yearlong mission aboard the International Space Station, Scott Kelly traveled over 143 million miles in orbit around Earth.
On average, Mars is 140 million miles away from our planet.
Coincidence? Well, basically.
NASA astronaut Scott Kelly took this selfie with the second crop of red romaine lettuce in August 2015. Research into things like replenishable food sources will help prepare the way for Mars. (And the red lettuce even kind of matches the Red Planet!)
There’s nothing average about a trip to Mars; so of course you don’t travel an “average distance” to get there. Launches for robotic missions – the satellites and rovers studying Mars today – are timed around when Earth and Mars are about a third of that distance, which happens every 26 months.
While the shortest distance between two points is a straight line, straight lines are hard to do in interplanetary travel. Instead, Mars missions use momentum from Earth to arc outward from one planet to the other. The Opportunity rover launched when Earth and Mars were the closest they’d been in 60,000 years, and the rover still had to travel 283 million miles to reach the Red Planet.
On the International Space Station, Scott Kelly was traveling at more than 17,000 miles per hour, an ideal speed for orbital research that keeps the station steadily circling Earth every 90 minutes. To break free of orbit and go farther to deep space, spacecraft have to travel at higher speeds. Opportunity, for example, traveled at an average of 60,000 miles per hour on the way to Mars, covering twice the distance Kelly traveled on the station in just over half the time.
Although Earth and Mars were relatively close together when Opportunity launched, the rover’s trip out was twice the average distance between the two planets.
The fastest any human being has ever traveled was the crew of Apollo 10, who hit a top speed of almost 25,000 miles per hour returning to Earth in 1969. For astronauts to reach Mars, we need to be able to propel them not only faster than the space station travels, but faster than we’ve ever gone before.
But the real lesson of Kelly’s year in space isn’t the miles, it’s the months. The human body changes in the absence of the effects of gravity. The time Kelly spent in space will reveal a wealth of new data about these changes, ranging from things like how fluid shifts in microgravity affected his vision to the behavioral health impacts of his long duration in the void of space. This information reveals more about what will happen to astronauts traveling to Mars and back, but it also gives us insight into how to equip them for that trip, which will be approximately 30 months in duration round-trip. What sort of equipment will they need to keep them healthy? What accommodations will they require to stay mentally acute? What sort of vehicle do we need to build and equip to send them on their journey?
Months and millions of miles. Momentum and mass. These are some of the most basic challenges of Mars. We will need to build a good ship for our explorers. And we will need the means to lift it from Earth and send it on its way fast enough to reach Mars.
An engine section weld confidence article for the SLS Core Stage is taken off the Vertical Assembly Center at NASA’s Michoud Assembly Facility in New Orleans.
While Scott Kelly has been living in space helping us to learn more about the challenges, we’ve been working on the rocket that will be a foundational part of addressing them. Scott Kelly left Earth last year half a month after the Space Launch System (SLS) Program conducted a first qualification test of one of its solid rocket boosters. Since then, we have conducted tests of the core stage engines. We’ve started welding together fuel tanks for the core stage. We’ve begun assembling the upper stage for the first flight. We’ve been building new test stands, and upgraded a barge to transport rocket hardware. The Orion program has completed the pressure vessel for a spacecraft that will travel around the moon and back. Kennedy Space Center has been upgrading the facilities that will launch SLS and Orion in less than three years.
And that’s just a part of the work that NASA’s done while Kelly was aboard the space station. Our robotic vanguard at Mars discovered evidence of flowing liquid water, and we’ve been testing new technologies to prepare us for the journey.
Down here and up there, it’s been a busy year, and one that has, in so many ways, brought us a year closer to Mars. The #YearInSpace months and millions of miles may be done, but many more Mars milestones are yet to come!
Next Time: Next Small Steps Episode 3
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You know how big the SLS vehicle will be. We described the tremendous power and thrust of just one of the RS-25 engines after last year’s test firings. You may have witnessed live as we fired one of the massive five-segment solid rocket boosters last March. Through all that, perhaps you can imagine how incredible it will be at launch when all four engines and both boosters ignite together to lift this 322 feet tall, 5.75 million pound rocket up through the atmosphere and toward deep space. Imagine the thunderous vibration in your chest even as you stand several miles away.
Note: Actually watching an SLS launch from this close is strongly not advised (or permitted). Orion hardware is being tested to withstand sound levels that would turn a person to liquid.
We’ve talked about how it will feel to be there when the rocket launches. Now, let’s talk about how it would feel to BE the rocket, launching.
Envision the power generated at launch as the engines and boosters throttle up to 8.8 million pounds of thrust. The heat is incredible! The vehicle starts to shake. The engine nozzles, as big and solid as they seem, will warp under the pressure of heat when the engines ignite seconds ahead of the boosters. While still on the pad, the boosters are bearing the weight of the entire vehicle even as they fire up for launch – the weight of almost 13 Statues of Liberty resting on an area smaller than an average living room.
Then, you – the rocket – are released to fly, and up you go. More than 5 million pounds of the weight of the rocket pushing down are now counteracted by more than 8 million pounds of thrust pushing from the opposite direction. Remember those 13 Statues of Liberty? Now the bottom of the rocket is feeling the pressure of 29 of them instead!
And now things are heating up on the front end of the rocket as well. Approaching Mach 1, shock waves move over the entire vehicle. Friction from just moving through the air causes the nose of the vehicle to heat. The shock waves coming off the booster nose cones strike the core stage intertank and can raise the temperature to 700 degrees. The foam insulation not only keeps the cryogenic tanks cold, it keeps the heat of ascent from getting into the intertank structure between the hydrogen and oxygen tanks.
Computer model of a shock wave at the front of the SLS vehicle at the time of booster separation during launch.
Are you feeling it yet? That’s a lot to handle. These impacts from weight (mass), pressure, temperature and vibration are called “loads.” It’s a key part of the “rocket science” involved in the development of the SLS vehicle.
A load is a pressure acting on an area. Sounds simple, right? There are all kinds of loads acting on SLS, some even before it leaves the launch pad. Tension and compression (pulling and pushing), torque (twisting), thermal (hot and cold), acoustic (vibration), to name a few. There are static (stationary) loads acting on the big pieces of the rocket due to gravity and their own weight. There are loads that have to be considered when hardware is tipped, tilted, rolled, and lifted at the factory. There are “sea loads” that act on the hardware when they ride on the barge up and down the rivers to various test sites and eventually across the Gulf of Mexico and up the Florida coast to Kennedy Space Center for launch. Engineers have to consider every single load, understanding how they will affect the structural integrity of the rocket and how they will couple and act together.
You’ve probably never thought of “riding on a boat” as rocket science, but SLS has to be designed to handle sea loads as well as space loads.
When SLS is stacked on the mobile launcher at KSC, there are loads acting through the four struts securing the core stage to the boosters and down into the booster aft skirts that have to carry the entire weight of the launch vehicle on the mobile launcher. Then there are roll-out loads when the mobile launcher and crawler take SLS more than 4 miles from the Vehicle Assembly Building to the launch pad. There are many more loads as the vehicle is readied for launch.
How do engineers know the rocket’s ready to handle the loads it has to face to send astronauts into deep space? Step One is good design – developing a rocket robust enough to withstand the strains of launch. However this is difficult as the vehicle needs to be as lightweight as possible. Step Two is digital modeling – before you start building, you run many, many simulations in the computer to a level of detail that would make any Kerbal Space Program fan jealous. Step Three is to do the real thing, but smaller – wind-tunnel models and even scale-model rockets with working propulsion systems provide real-life data. And then comes Step Four – build real hardware, and stress it out. Test articles for the core stage and upper stage elements of the vehicle will be placed in test stands beginning this year and subjected to loads that will mimic the launch experience. Engines and boosters are test-fired to make sure they’re ready to go.
Still want to be the rocket? Stay tuned for more on loads as we do everything possible to shake, rattle, and yes, even roll, the pieces of the rocket, ensuring it’s ready to launch in 2018.
Next Time: No Small Steps Episode 3
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2016 is well underway. Another year over, another year begun.
For the SLS program, it means we’re even further past the halfway point toward launch readiness. It’s been only four years since the program officially began in September 2011, and we’re working toward being ready in less than three years for our first launch.
The day this is a photograph instead of an artist’s concept will be a good day.
The bulk of the first four years was focused on completing the design. To be sure, there was smoke and fire and bending metal as we tested boosters and engines and began building the barrels for the core stage of the rocket. Building on the foundation of the Space Shuttle Program allowed us to move quickly into testing of the engines and boosters, and the design work on the core stage progressed rapidly enough to allow us to begin early manufacturing, and all of that was preparation for what would come when we completed the critical design review of the plans.
RS-25 Engine 2059 is currently in the stand for testing at Stennis Space Center. A few years ago, it powered Atlantis’ longest mission, and a few years from now, it will loft SLS’ first crew into space.
With the design work all but done, the push toward the pad is well underway, and there’s a lot of work that entails.
For the rocket to roll out to the pad for launch, each element of the vehicle has to arrive at the Vehicle Assembly Building at Kennedy Space Center to be stacked together with the Orion crew vehicle. And each part has its own road to get there.
For the upper stage portion of the vehicle, which will push Orion out of Earth orbit and into deep space, to be ready to fly, test articles will be built of the adapters that connect the upper stage to the rest of the rocket and to Orion, along with a test article of the upper stage itself. These three test articles will be placed in a stand together, and subjected to stresses and strains to make sure they’re ready for launch. Based on the results of that test, the actual flight articles of the upper stage and adapters will be completed and transported from Marshall Space Flight Center in Huntsville, Ala., to Kennedy Space Center.
For the solid rocket boosters to be ready to fly, qualification motor tests will take place at Orbital ATK in Utah. The results of those tests will pave the way for processing, fueling and completion of the flight boosters, using hardware already at Kennedy Space Center. The boosters will be the first piece of SLS to be stacked in the VAB at Kennedy.
For the 200-foot-tall core stage, which its large fuel tanks and RS-25 engines to be ready to fly, the engines and the stage itself must each undergo individual preparation, and then be integrated together. Tests will be conducted at Stennis Space Center in Mississippi of individual engines, to make sure the RS-25 is ready for the environment it will encounter during launch. Test articles will be built of the large pieces that make up the core stage, and will be transported from Michoud Assembly Facility outside New Orleans to Marshall, where they’ll be placed in large test stands – which have to be built for this purpose – to undergo structural testing. Using the results of those tests, the actual first flight core stage will be completed. Engines will be transported from Stennis to Michoud to be integrated into the core stage, which will then be transported back to Stennis for the largest rocket test firing since the Apollo era. Once it has been tested, the stage will then be shipped down to Kennedy for stacking.
And that’s just the big pieces. In the meantime, work must be done on things like making sure the software that controls the rocket is ready to go.
At Marshall Space Flight Center, work is taking place now on the stands that will be used for the test versions of core stage components.
We’ve already made a good start on this “building” phase of the program. In March of last year, we conducted the first qualification test of the solid rocket boosters, and we’re currently preparing for the next, which will take place later this year. At the same time, we’ve started working on the flight hardware for the boosters for SLS’s first launch.
We’ve completed the first series of individual engine tests, using an unflown development engine, and are about to start the second early this year, using an engine that has flown on shuttle missions and will fly again on the second flight of SLS.
We’re almost finished with the upper-stage element test articles, and will use them to conduct structural tests over the course of this year. At the same time, work has already begun on the actual upper stage that will be used to push Orion beyond the moon on SLS’s first flight.
We’re well underway building the pieces that will be used to finish the core stage test articles and the stands on which they’ll be tested. Very soon, we’ll be welding together test articles of the rocket’s liquid hydrogen and liquid oxygen tanks, as well as other core stage components. Those, in turn, will be followed by the flight articles for the first core stage.
It’s an exciting time, and making it more exciting is the fact that this work is taking place in the modern era of digital media, giving you an unprecedented look at the process. As we continue to grow closer, one step at a time, to launch, you’ll be able to follow us every step of the way.
Next Time: May The Forces Be With You
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What do NASA’s Orion spacecraft and nuclear-powered airplanes have in common? Here’s a hint: It’s something they also both have in common with actor Samuel L. Jackson.
The answer, of course, is that they’ve all been to NASA’s Plum Brook Station in Sandusky, Ohio.
The piece of hardware on the left fits roughly were the NASA logo is on the rocket to the right.
Plum Brook, a branch of NASA’s Glenn Research Center, was originally created to allow the agency to conduct nuclear research, first related to airplanes and then to nuclear rockets. Today, it’s a unique facility that allows testing that replicates extreme conditions encountered in spaceflight – from vacuum and thermal environments found in orbit to launch-like acoustic levels that would turn a human body into a puddle.
On an average day, the Space Power Facility at Plum Brook is engaged in tasks like using a a vacuum chamber made of aluminum equivalent to about one billion soda cans to test large payload fairings for SpaceX rockets. And on special occasions it’s used for more unique purposes, like serving as a set for Marvel’s The Avengers (in case you’ve ever wondered why there was a NASA banner hanging behind Jackson’s Nick Fury in the opening scene).
I had the opportunity to visit Plum Brook last month for the arrival from Europe of a test article of the Orion crew vehicle’s service module.* Orion, of course, is the aforementioned deep-space spacecraft, which will be launched on SLS to enable human missions beyond the moon and eventually to Mars. Orion is designed to meet the robust demands of human space exploration, from providing life support to keep up to six astronauts healthy and safe to withstanding the high temperatures generated by a high-speed entry into Earth’s atmosphere.
In order to do that, Orion has requirements that dwarf those of a mission to low Earth orbit. Even after it separates from SLS, Orion will need more than twice as much propellant as a spacecraft on an orbital mission. It will have to have four times the ability to scrub carbon dioxide from the atmosphere, and will have to carry five times as much oxygen and drinking water.
Just some of the ways Orion is designed uniquely for a unique purpose.
Which is where the service module comes in. It’s a combination of a propulsion system and a storage unit for all those helpful things like air and water that keep astronauts alive while traveling hundreds of thousands of miles from home. Orion’s service module is provided by the European Space Agency, in a partnership agreement that has its roots in NASA’s cooperation with ESA on the International Space Station. The service module builds on the success of the European Automated Transfer Vehicle, which has carried cargo to the space station since 2008.
Work is well underway on the service module for the first flight of SLS and Orion on Exploration Mission 1, but, in the meantime, the recently arrived test article will be put through a variety of stresses and loads to make sure the design is ready to fly. Being at the event marking the arrival of the test article was a glimpse into the future of international space exploration – an overlapping of different accents and different languages, united in a common message of working together to do things we’ve never before done.
The Red Planet is waiting. And people from around our planet are already working together to get there.
The acoustic test chamber at Plum Brook will subject the test article to 163 decibels of sound.
*If you’d like to join Orion and Samuel L. Jackson in having a Plum Brook connection, your chance is coming. Plum Brook Station and Glenn Research Center, in Cleveland, will hold open houses in 2016, on June 11-12 and May 21-22, respectively, in connection with Glenn’s 75th anniversary.
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These are actors from a video about the first launch of Orion. The actual roles of “Orion crew members” are yet to be cast.
Many moons ago, an Orion program executive asked on a Twitter chat what advice he would have for the first crew that will fly on the spacecraft the team is building.
The answer could have gone in any number of directions, from how the steering’s going to handle to what to pack for the trip. But what he said was this:
“Hang on! You’re about to make history!”
For me, that response was a good reminder – it’s one thing to remember the historic significance of the first crewed flight of Orion and SLS as a huge stepping stone in human exploration of the solar system, but it’s another thing altogether to appreciate that step as an incredibly unique experience for the individuals involved. When the crew returns to Earth at the end of the mission, they will share stories of what it was like to have the personal experience of looking past the moon and seeing our home planet in the distance beyond.
Others will follow them, and come back with their own incredible stories – living long periods farther from Earth than anyone ever has, voyaging deep into the expanses of space, being the first to interact with raw relics of the formation of our solar system floating in the void. And as those pioneers carry us farther in our journey to Mars, others will remain closer to home, performing revolutionary scientific research aboard the International Space Station.
Not long after that Twitter chat, I was privileged to sit in on a briefing about SLS to a unique audience: NASA’s 2013 class of astronaut candidates. It was interesting to watch them as the presenter talked about the rocket we’re building. At the end of the presentation, they were shown a video – an animation of a crewed launch of SLS and Orion. The video included a scene of a crew walking out to board the vehicle, and, to be honest, I was a little envious watching the future astronauts realize it would be them who would be doing that in real life, seeing them get excited about the possibilities and opportunities that lay before them.
But that moment was also a healthy reminder – we’re building this rocket to carry these people, and others like them. SLS and Orion will open the solar system for exploration by humankind, but will do so by carrying not faceless representatives of our species, but by safely transporting real individuals through the unmatched fires of launch and the unrelenting void of space and the unforgiving heat of entry. It is our job to give them a good ship for the journey.
Spacesuit engineers demonstrate how four crew members would be arranged for launch inside the Orion spacecraft, using a mockup of the vehicle at Johnson Space Center.
And that focus permeates everything we do. When NASA founded the SLS program, one of our key tenets was safety. Before we built, the vehicle was modeled on computers and in small scale. We test the engines and boosters again and again and again. Flight hardware is preceded by test articles that are subjected to incredible stresses to see how they will withstand the dynamic pressures of launch. Where possible, redundancy is included to add an additional level of safety. Contingencies are identified and preparations are made. Spaceflight is an endeavor that will never be without risk. We carry the responsibility of equipping pioneers to face that risk as safely as possible.
Today, NASA is looking for the next group of men and women that will carry forward our work in space, both aboard our outpost science laboratory in Earth orbit and on the proving ground missions that will prepare for missions to Mars, flying on a new fleet of American spacecraft including not only SLS and Orion but also Commercial Crew vehicles.
If you want to apply to be an astronaut, among the credentials you’ll need are a bachelor’s degree in engineering, biological, physical or computer science or mathematics and at least three years of related professional experience, or at least 1,000 hours of pilot-in-command time in jet aircraft. Visit USAJobs.gov and search for the keyword astronaut to apply online.
And for those who are selected, we’re working hard to build you a great ship. Hang on, you’re about to make history!
Next Time: An Orion Overview
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Aluminum is the most abundant metal on Earth. It’s also highly reactive. Aluminum is so reactive, in fact, that it’s not found naturally in its pure form but only in combination with other minerals. It’s this ability to readily combine with other metals that makes aluminum so useful. Every day, we use products made of aluminum alloys, or mixes with other metals, for things like beverage containers, covering leftovers, or iPhones. Amazingly, it’s this same stuff that fuels solid rocket boosters.
This reaction heats the inside of the solid rocket boosters to more than 5,000 degrees Fahrenheit, causing the water vapor and nitrogen to rapidly expand. Just like in the liquid engines, the nozzle funnels the expanding gases outward, creating thrust and lifting the rocket from the launch pad.
