All Roads Lead to the Pad

An RS-25 engine is delivered by flatbed truck to a test stand at Stennis Space Center.
A large truck can transport a rocket component the size of one engine. But how do you transport a piece as tall as, say, the Leaning Tower of Pisa?

NASA is preparing for the first of many flights of the agency’s Space Launch System rocket and Orion spacecraft. Every day we’re making progress toward their first integrated test flight. Today, that work is taking place at numerous sites around the country, but the work of that nationwide team is firmly focused on one place – the launch pad.

Hundreds of companies across every state have been a part of SLS and the Orion crew spacecraft, many of them small businesses providing specialized components or services. That work comes together at NASA and prime contractor facilities where the “big pieces” are assembled before it all comes together on the launch pad at NASA’s Kennedy Space Center in Florida.

A crane lifts the ICPS test article out of a shipping container.
A test article of the Interim Cryogenic Propulsion Stage was delivered to Marshall Space Flight Center from United Launch Alliance in June.

1) Second Stage, From Alabama to Florida by Barge

Some of the pieces have a relatively direct route to the launch pad. At Marshall Space Flight Center in Huntsville, Alabama, where the SLS program is managed, for example, the flight unit for the Orion Stage Adapter (OSA) that will connect the SLS second stage to the crew spacecraft is being welded, and welding will begin next month on the Launch Vehicle Stage Adapter (LVSA) that will connect the core and second stages. When completed, the LVSA will travel by barge to the gigantic Vehicle Assembly Building (VAB) at Kennedy Space Center (KSC) in Florida, where final stacking of SLS and Orion will take place. The smaller OSA has the option of barge or truck, and after arriving in Florida, will make a stop at a facility where 13 CubeSats will be installed before continuing on to the VAB.

Half an hour away, the second stage of the rocket, the Interim Cryogenic Propulsion Stage (ICPS), is being completed at the United Launch Alliance facility in Decatur, Alabama. The process for the ICPS will be one step longer – after being barged from Decatur to Florida, the stage will be prepared for flight at a payload processing facility before being moved to the VAB for stacking.

Booster segments being delivered by train to Kennedy Space Center during the space shuttle era
Booster segments being delivered by train to Kennedy Space Center during the space shuttle era.

2) Boosters, From Utah to Florida by Train

Propellant is already being cast into booster segments for the first flight of SLS. The boosters will be transported by train from an Orbital ATK facility in Utah to Florida. Since the 17-story-tall boosters are far too long to be transported in one piece, the boosters will be transported in segments. They’ll arrive at a processing facility at Kennedy before being moved to the VAB where they’ll be stacked vertically and joined by the rest of the rocket.

Cutaway view of the core stage inside the Pegasus barge
NASA’s large Pegasus barge will be able to transport the SLS core stage, which will be more than 200 feet long.

3) Engines and Core Stage, From Mississippi to Louisiana to Mississippi to Florida By Barge

This one’s a little more complicated. RS-25 core stage engines are currently in inventory at Stennis Space Center in Mississippi, where engine testing is taking place. The core stage hardware for the first launch of SLS is currently being welded at Michoud Assembly Facility in New Orleans. The engines for the first flight will be transported from Stennis to Michoud, and integrated into the first core stage when it’s completed. The core stage with engines will then be transported back to Stennis, where the 212-foot-tall stage-and-engine assembly will be placed into a test stand and all four engines will be fired together in the largest liquid-engine ground test since Apollo. After the test, plans call for the stage to be shipped to Kennedy by barge, where it will be brought to the VAB for assembly with the rest of the rocket.

Artist concept of SLS and mobile launcher on the crawler transporter.
The crawler-transporter is capable of transporting 18 million pounds from the VAB to the launch complex.

4) Rocket, From VAB to Launch Pad via Crawler

Once all of the elements have arrived at the VAB, they’ll be stacked vertically and prepared for launch. The large crawler transporter will bring the mobile launcher with tower to the rocket, and will then carry rocket and launcher together to the launch pad. Which leaves only one last step:

5) Orion, From Launch Pad to Deep Space, via Rocket

NASA is on track for the first mission to launch no later than November 2018 from Florida. The first test flight of SLS and Orion will be incredible, and it will pave the way for our second exploration mission – our first with crew aboard the spacecraft. As these missions continue to come together, we’re closer to sending astronauts to Red Planet than at other point in our history. All the work we’re doing together today will continue to enable that journey in the future.

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Behind the Scenes at QM-2: Getting Ready to Test the World’s Largest Solid Rocket Motor

By Beverly Perry

For two monumental minutes on June 28, the Space Launch System (SLS) solid rocket boosters — the largest ever built for flight — will fire up in an amazing display of power as engineers verify their designs in the last full-scale test before SLS’s first flight in late 2018. Each piece of hardware that’s qualified and each major test — like this one, dubbed QM-2 — puts NASA one step closer on its Journey to Mars.

The smoke and fire may last only two minutes, but engineers at NASA’s Marshall Space Flight Center in Huntsville, Alabama and Orbital ATK in Promontory, Utah have been preparing weeks — even months — in advance for the static test of Qualification Motor 2 (QM-2). Here’s a behind-the-scenes look at what goes into getting ready to fire up the largest and most powerful solid rocket motor ever built for flight.

T (for test) minus weeks and months. In the months prior to the test, propellant-filled segments began arriving at Orbital ATK’s Test Bay T-97 after being cast in nearby facilities. Many of these segments are veterans of space shuttle flights. In fact, the various metal case segments that comprise the five-segment QM-2 motor flew on 48 shuttle flights!

T minus 14 days. In the two weeks leading up to the test, Orbital ATK engineers begin dry runs that simulate the final test as closely as possible (without the smoke and fire). They put the motor and associated systems through their paces no fewer than 11 times before the big day to ensure not only that all systems are functioning as expected, but also that the test will be executed properly. “We only get one shot at firing the rocket motor,” says Dr. Janica Cheney, Orbital ATK’s director of Test Operations. “All the dry runs and other preparations that take place ahead of time are critical to ensuring we get the data we need from this test firing.”

NASA and Orbital ATK test SLS Qualification Motor-2 (QM-2) before first flight.
Are you ready? It’s time for the final full-scale test before the first flight test of the SLS solid rocket motor June 28 at 10:05 a.m. EDT (8:05 a.m. MDT). Many cameras record data during the test, such as this one which captures nozzle plug performance during the test.

T minus 24 hours. For this final full-scale static test, engineers have 82 goals, or test objectives, they need to measure and evaluate. One day before the test, it’s crunch time; caffeine’s flowing as engineers work around the clock the day before the test to ensure all systems function properly and all necessary data can be collected.

T minus 8 hours. Game day. There’s focus — and excitement. There are two more dry runs leading up to the test. Engineers, technicians and operators are “on station,” — present and accounted for at key locations such as the test bay, the instrument rooms and the control bunker. When you hear “control bunker,” think mission control — a command and control center that directs every aspect of the test, similar to what you see at mission control during a launch. Time flies during the final eight hours before the test.

Orbital ATK’s Test Bay housing rolls back to reveal Qualification Motor-2 (QM-2).
At T minus 6 hours with a “go” decision for testing QM-2, engineers at Orbital ATK will roll back the booster test bay housing so the massive motor can be fired.

T minus 6 hours. At 4:05 a.m. EDT (2:05 a.m. MDT), engineers and managers at Orbital ATK and NASA will make a “go” or “no go” decision on testing that day. Assuming the test’s a go, technicians “roll back” Orbital ATK’s specially designed moveable test bay housing and begin running final checks to make sure everything is ready. “We check the status of all the data and control systems, the test bay, the motor preparation and weather conditions,” Cheney says.

Weather is one variable that can halt the QM-2 test. “We make sure there’s no lightning in the area; no high winds; no storms,” explains Orbital ATK Fire Chief Blair Westergard. “We also establish fire breaks. Along with the Box Elder County Fire District, we’re prepared to extinguish any secondary wildfires too.”

Engineers also make sure cameras are ready to film and all data recording systems are online and functioning properly. Orbital ATK Security ensures the area around the test is clear.

T minus 3 hours. Crowds begin to gather as the public viewing area near Promontory off State Route 83 opens at 7:30 a.m. EDT (5:30 a.m. MDT). Orbital ATK Security directs traffic with the help of the Utah Highway Patrol and provides crowd control support to ensure everything remains orderly — vital when 10,000 people are in attendance.

https://www.youtube.com/watch?v=c-xrhYKC0q4[/embedyt]

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

T minus 1 hour. The formal countdown commences; the public address system broadcast begins. The crew in the test bay begins final procedures to prepare the booster for testing.

T minus 9 minutes. Final system and timing checks are underway.

T minus 4 minutes. A “go for test” announcement sounds from the public address system.

T minus 1 minute. A siren begins; it will blare through T minus 20 seconds.

T minus 45 seconds. The “Safe and Arm” system sequence begins, which arms the motor. The Safe and Arm device is remotely activated from the “safe” position into the “armed” position, allowing the motor to ignite when the “fire” command is given.

T minus zero. At 10:05 a.m. EDT (8:05 MDT), two minutes of pure awesome commence as the gigantic motor burns through about five and a half tons of propellant each second during the approximately two-minute test. Inside the control bunker, there will be jubilation — and relief. “This is serious business — this is rocket science,” Cheney emphasizes. “But there’s nothing better than the smoke and fire and the data that comes with it when you’ve had a successful day. Our success is NASA’s success — we don’t do it alone.”


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Small Hitchhikers Ride through the Galaxy

By Beverly Perry

On the first launch of the Space Launch System (SLS), America’s next-generation heavy-lift rocket, the Orion Stage Adapter (OSA) will carry 13 CubeSats, or boot box-sized science and technology investigations, that will help pave the way for future human exploration in deep space. Engineers and technicians at NASA’s Marshall Space Flight Center have built the main structure of this hardware that will be part of the rocket when it lifts off from Launch Complex 39B at NASA’s modernized spaceport at Kennedy Space Center in Florida.

The Orion Stage Adapter being designed and manufactured at NASA’S Marshall Space Flight Center in Huntsville, Ala. nears completion.
Jennifer Takeshita, the lead for friction stir welding at Teledyne Brown Engineering, compares a model of the Orion Stage Adapter (OSA), including brackets to secure CubeSats during their spaceflight, to the flight hardware nearing completion at Marshall Space Flight Center.

The Orion Stage Adapter does exactly what its name indicates: it connects the Orion spacecraft to the second stage of the launch vehicle. Using enormous friction-stir welding machines, engineers just finished welding three large panels into a ring that is 18 feet in diameter and 5 feet high. With this welding complete, it’s time for analysis. The main structural ring is currently undergoing nondestructive analysis using 3-D structured light scanning and photogrammetry, which creates a computer model using photography, to ensure hardware was built to design specification.

Three-dimensional structured light scanning, photogrammetry, and solid modeling software are helping engineers visualize the minute differences between the OSA that was designed and the hardware that was built.
Engineers use 3-D structured light scanning and photogrammetry to analyze the main structure of the Orion Stage Adapter (OSA) at Marshall Space Flight Center. Targets for the optical scanner and SLR camera can be seen on the aluminum structure. Solid modeling software will combine the images into a single computer model so engineers can compare finished hardware to the design.

Next, engineers will trim it, weld upper and lower rings onto the large ring, machine it to final dimensions, apply paint, and install the diaphragm, a barrier that separates SLS from Orion. After that, installation of cables and the brackets that will secure the secondary payloads during their spaceflight will complete this critical piece of flight hardware.

The 13 CubeSat secondary payloads will be some of the first small satellites to explore deep space and answer critical questions relevant to NASA’s future exploration plans. These small but mighty scientific investigations include ten satellites from U.S. industry, government, and commercial partners as well as the three CubeSats being built by international partners.


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The Rocket Comes to the Rocket City

By David Hitt

Over the next year, the rocket comes to the Rocket City in a big way.

Huntsville, Alabama, a.k.a. “Rocket City,” is home to NASA’s Marshall Space Flight Center, where today the Space Launch System (SLS), the powerful rocket NASA will use for human exploration of deep space, is being developed.

More than six decades ago – before NASA even existed – Huntsville laid claim to the nickname thanks to its work on missiles and rockets like the Juno that launched the first American satellite or the Redstone used for the first Mercury launches.

In the years since, Huntsville, and Marshall, have built on that legacy with work on the Saturn V rockets that sent astronauts to the moon, the space shuttle’s propulsion systems, and now with SLS.

New test stand at Marshall Space Flight Center
A steel beam is “flown” by crane into position on the 221-foot-tall (67.4 meters) twin towers of Test Stand 4693 during “topping out” ceremonies April 12 at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

While the program is managed at Marshall Space Flight Center, contractors around the country are building the rocket. Engines are being tested in Mississippi. The core stage is being built in Louisiana. Booster work and testing is taking place in Utah. Aerospace industry leaders and more than 800 small businesses in 43 states around the country are providing components.

The Marshall team has also been involved with the hardware, largely through testing of small-scale models or smaller components. The center also produced the first new piece of SLS hardware to fly into space – a stage adapter that connected the Orion crew vehicle to its Delta rocket for Exploration Flight Test-1 in 2014 (See Orion’s First Flight for more.) The same adapter will connect Orion to SLS for their first flight in 2018.

The top half of a test version of the SLS Launch Vehicle Stage Adapter on a weld tool at Marshall
Workers prepare the top half of a test version of the SLS Launch Vehicle Stage Adapter. The completed adapter will undergo structural testing at Marshall later this year.

Now, however, big things are happening in the Rocket City. The new Orion stage adapter for the upcoming launch is being built. The larger Launch Vehicle Stage Adapter, which will connect the core and second stages of the rocket, is being built at Marshall by contractor Teledyne Brown Engineering. This year, test versions of those adapters and the Interim Cryogenic Propulsion Stage (ICPS) will be assembled into a 56-foot-tall stack, which will be placed in a test stand to see how they handle the stresses of launch.

Those test articles built locally will be joined by larger ones produced at the Michoud Assembly Facility outside New Orleans. Test versions of the rocket’s engine section, oxygen tank and hydrogen tank will be shipped by barge from Michoud to Marshall. Two new test stands – one topped out last month at 221 feet tall – have been built at Marshall, joining historic test stands used to test the Saturn moon rockets.

The Payload Operations Center at Marshall Space Flight Center
In addition to rocket development, Marshall is involved in numerous other efforts, including supporting all U.S. scientific research conducted aboard the International Space Station.

Fifty-five years ago this month, Alan Shepard became the first American in space riding on a Redstone rocket, named for the Huntsville army base where his rocket had been designed – Redstone Arsenal. Today, Marshall, located on the same red clay that gave the arsenal and rocket their name, is undertaking perhaps its largest challenge yet – building a rocket to carry humans to the red stone of Mars.

Huntsville grew substantially from its small Southern town roots during its early days of rocket work in the 1950s and ‘60s, and Marshall has gone on to be involved in projects such as Skylab, Spacelab, the Hubble Space Telescope and the International Space Station, to name a few. But despite branching out its work both in space and other technology areas, Huntsville remains the Rocket City.

…After all, we built this city on a rocket role.


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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.

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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]

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Next Time: We’ve Got Chemistry!

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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.

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#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

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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

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