We’ve Got (Rocket) Chemistry, Part 2

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.

Artist rendition of boosters and engines of during launch
The powerful aluminum-ammonium perchlorate reaction fuels the twin SLS solid rocket boosters.

Aluminum doodleAluminum 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.

: Interior of booster case after firing
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.

Nitrogen doodleThis 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.


Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

We’ve Got (Rocket) Chemistry, Part 1

Written by Beverly Perry

What do water and aluminum have in common?

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.

RS-25 engine during testing
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 doodleHydrogen, 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.

Oxgen doodleAlthough 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.

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

Five “Secrets” of Engine 2059

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 during testing at Stennis Space Center on March 10
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.

Launch of Atlantis on STS-125
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.

View of the test stand during the test of engine 2059 at Stennis Space Center on March 10.
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!

Infographic about engine testing
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.

NASA Social attendees with engine 2059 in the background
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 enginesnone 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.

Watch the test here:
https://www.youtube.com/watch?v=njb9Z2jX2fA[/embedyt]

If you do not see the video above, please make sure the URL at the top of the page reads http, not https.


Next Time: We’ve Got Chemistry!

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

Time Flies: Next-Generation Rocket Is the Work of Generations

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.

Kathryn Crowe and Hugh Brady
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.

Illustration showing the Block 1B configuration of the rocket and 8.4 and 10 meter payload fairing options
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.”

https://www.youtube.com/watch?v=gXMhOe1pRKc[/embedyt]If you do not see the video above, please make sure the URL at the top of the page reads http, not https.


Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

Making a Lot of Fire in Two “Easy” Steps

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.

Close-up of aft end of SLS during launch
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.

http://youtu.be/zJXQQv9UZNg[/embedyt]
If you do not see the video above, please make sure the URL at the top of the page reads http, not https.


Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

#YearInSpace: Mars, Miles, Months, Mass and Momentum

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.

Scott Kelly with plant-growth experiment
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.

Graphic showing Opportunity’s trajectory from Earth to Mars
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
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

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

Think You’re Stressed? Try Being A Rocket

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.

Artist’s concept of an SLS launch
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.
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.

The Pegasus barge that will transport SLS
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

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

What’s A Spacecraft Factory Like? Think Big!

“I’ve been to the Smithsonian,” said one awed observer. “I’ve seen crew capsules before. They’re not that big!”

Last month, welding concluded on the pressure vessel, the basic structure of the Orion deep-space crew vehicle. Workers from around the country who had prepared components and materials for the spacecraft were invited to NASA’s Michoud Assembly Facility outside New Orleans to see the culmination of their labor before it was transported to Kennedy Space Center in Florida for completion.

The Orion team at the Michoud Assembly Facility poses with the Exploration Mission 1 crew module pressure vessel
The Orion team at the Michoud Assembly Facility poses with the Exploration Mission 1 crew module pressure vessel prior to its transfer to the Kennedy Space Center ,where it will undergo final assembly in preparation for flight in 2018.

Even to those who helped build it, and even in that unfinished state, Orion was an impressive sight. Workers found themselves standing feet away from the core of a spacecraft that will travel around the moon, farther into space than Apollo ever went, and then return to Earth; hardware that they had helped create. And even though they had seen components of it, some expressed surprise at the size of what they’d helped build.

From a big crew vehicle to a big rocket to “the world’s largest dishwasher” (What’s that? Keep reading) “big” was the word of the day when the team at Michoud marked the completion of welding of the pressure vessel for the first Orion capsule to fly on a Space Launch System (SLS) rocket.

It was … well, a big deal.

Which is appropriate, because Michoud Assembly Facility is a big place. Originally built in 1940 to produce plywood airplanes for World War II, Michoud is one of the largest manufacturing plants in the world, with the main facility covering 43 acres under one roof. Michoud became a NASA facility in 1961. Among its contributions, Michoud produced stages for Saturn V rockets, and the external tanks that fueled every space shuttle flight.

The Orion pressure vessel at Kennedy Space Center
The Orion pressure vessel has now arrived at Kennedy Space Center, where it will be outfitted for its next mission, going beyond the moon.

Today Michoud is a multi-user facility, with government and commercial tenants. Walk through Michoud, and as you begin to understand just how big 43 acres is. As you come in, you see state-of-the-art tooling being used for Orion and SLS. Venture even farther, and you find private companies making use of the factory’s diverse array of equipment including some of the same tools that sent men to the moon. (The factory is also home to some big movies – just recently, filming has taken place there for “Jurassic World” and “Dawn of the Planet of the Apes,” among others.)

How big is Michoud? The factory is so large that if you don’t know what you’re looking for, you could walk through and totally miss the largest spacecraft welding tool in the world – not because it’s easily missed, but because it’s set apart from the main floor in its own separate chamber, behind one of many bay doors and a couple of mundane-looking doorways. Enter the chamber, however, and there is nothing mundane about the 170-foot-tall Vertical Assembly Center, a new tool built custom for SLS. Into the VAC are placed 27.6-foot diameter barrels, domes and rings, and it welds them together into giant fuel tanks for the SLS core stage. Then they go in the “largest dishwasher,” as SLS core stage manager Steve Doering referred to it at the event, a piece of equipment on the other side of the chamber that washes them post-welding.

Overhead view of the Vertical Assembly Center and a welded barrel stack
Core stage barrel sections are now being welded together to form fuel tank test articles in the Vertical Assembly Center at Michoud.

On the day of the event, visitors to the chamber of the Vertical Assembly Center were greeted by its first product – a stack of two barrels, about 40 feet high, which filled the entrance to the VAC chamber. By itself, the stack looms over visitors as they approach it, but it invites a quick mental calculation: The core stage of SLS will be five times taller still than that. And that’s still less than two-thirds the height of the entire rocket. It’s big.

Orion then traveled to Kennedy Space Center to be outfitted as a cutting-edge spacecraft. At the same time, the SLS fuel tanks are in production at MAF and will undergo testing before a complete SLS core stage is test fired and shipped to Kennedy as well. There, the core stage and the SLS boosters and upper stage will join Orion for stacking and then launch.

And that will be one really big day.


Next Time: Think You’re Stressed? Try Being A Rocket

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

The Next Steps Are Here

Back in November, we debuted the first in a set of new videos, “No Small Steps.” Now, the next “Steps” is here!

The first video in the series explained why going to Mars is a very big challenge, and why meeting that challenge requires a very big rocket. (Hint: You need a whole lot of fuel.)

The second installment goes a step further, by discussing how NASA’s Space Launch System (SLS) builds on the foundation of the Saturn V and the Space Shuttle, but then uses that foundation to create a rocket that will accomplish something neither of them could – sending humans to the Red Planet.

Illustration showing a Saturn V and SLS launch, with the text The physics of sending a rocket into space haven’t changed, but our engineering has.SLS takes advantage of some of the best concepts and systems from its predecessors. Like the Saturn V, SLS is a massive, staged rocket. Like the space shuttle, it uses solid rocket boosters and RS-25 engines. But unlike either of those vehicles, SLS will be able to support human missions to Mars. How do you combine elements of two different vehicles and produce a new one with a capability neither of the others had? You take the best of yesterday and INNOVATE.

Today’s teams have the added advantage of a few decades of technology development. The teams that built the Saturn and Shuttle were pioneers of rocket science, but today we’ve not only built on their foundation but also improved on things like welding science.

And while they may not be as glamorous as making smoke and fire, advances in things like modeling and analysis, welding techniques and software development add up to be a very big deal.

Why? Because on the journey to Mars, there are No Small Steps.

https://www.youtube.com/watch?v=DesBgDPR22Q[/embedyt]


Next Time: Visiting the Rocket Factory

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!

The Path to the Pad

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.

Artist’s concept of SLS stacking at Kennedy Space Center
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.

An RS-25 engine being raised into the test stand
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.

A new SLS test stand being built at Marshall Space Flight Center
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

Join in the conversation: Visit our Facebook page to comment on the post about this blog. We’d love to hear your feedback!