Journey to Mars – Page 3 – Rocketology: NASA’s Space Launch System

The Journey to Mars!

A graphic showing an astronaut above the Mars horizon with a rover on the surface — NASA’s Journey to Mars is not simply a human exploration mission; it will bring together much of the best of what NASA does.

How do you get to Mars? You build a rocket, and go.

OK, it’s actually a bit more complex than that. A lot more complex, really. But that’s still a vitally important step. We’ll come back to why in a minute.

First, let’s talk about that “complex” part.

Mars is hard. Really hard.

To start with, Mars is far, far away. At its closest, it can come within 34 million miles of Earth, but that’s a once-in-millennia approach. Usually, if the distance gets within the low 50s, that’s really close. At farthest, Mars is about 250 million miles away. Distance means it takes time to get there.

As you travel that distance, there’s a giant ball of gas in the center of the solar system that really wants to kill you. Once you leave Earth, you’re being constantly bombarded with radiation from our own sun and distant stars.

Then there’s the fact that, if you wanted to design a planet that would be hard for humans to land on, Mars would be a good start. The atmosphere is thick enough to combine with the gravity to make an Apollo-style powered descent difficult, but it’s too thin to make a Shuttle-style glide or Orion-like parachutes easy.

Once you make it past the distance, through the radiation, and to the surface, Mars is still inhospitable. Back in 1972, following a detailed survey of planetary conditions, noted Mars expert Elton John summarized that it ain’t the kind of place to raise your kids, and for the moment that’s not a bad assessment.

All of these challenges are substantial. All of these challenges can be overcome.

A graphic explaining NASA’s three-phase Journey to Mars through Earth Reliant, Proving Ground and Earth Independent phases — Not only is NASA’s Journey to Mars the most ambitious mission the agency has undertaken, it will consist of a series of stepping stones that will also be some of the most ambitious missions we’ve ever flown.

NASA’s Journey to Mars is a holistic approach to solving those challenges, to landing humans on Mars, and to answering key scientific questions about Mars, its environment, its history and its habitability.

This Journey is not something NASA is planning to do; it’s something we are doing, right now, in numerous ways, combining the best of our experiences and abilities in a variety of fields.

Robotic explorers are today orbiting the planet and driving across its surface, teaching us more about the conditions there in order to answer those scientific questions and help us prepare for human exploration.
Astronauts aboard the International Space Station are conducting research regarding living in space for the long durations a Mars mission will require, learning more about how to maintain both equipment and the human body during the journey.
Scientists and engineers are working to mature the advanced technologies that will be needed to solve the complex challenges like radiation protection and entry through the Martian atmosphere.
We are also building the robust systems that we need to carry out the trip. The Exploration Flight Test-1 of the Orion crew vehicle in December 2014 was a major milestone, and the first flight of Space Launch System will be another. Later will come in-space propulsion systems, deep-space habitats, and more.

A photo of a rover wheel track on Mars that resembles a human footprint — An important thing to keep in mind when talking about Mars exploration is that we’re already there. This “footprint” photo was captured by the Spirit rover of a track left by one of its wheels, and is a good reminder that our robot explorers are already taking “first steps” on the Journey to Mars.

We’re still in the early phases of the Journey, when our human spaceflight is still “Earth-Dependent,” relying on the supply line and other benefits that come from proximity to our home planet.

Soon, we will begin a series of increasingly ambitious “Proving Ground” missions, traveling farther into space and testing new systems and capabilities.

Finally, when we’ve demonstrated we can be “Earth-Independent,” we’ll be Mars-ready. It will be time to take the next giant leap – possibly first into Mars orbit or the Martian moons, and ultimately to take our first steps on the surface of another planet.

Which brings us back to how you get to Mars – You build a rocket, and go.

All of those challenges will ultimately be solved with hardware – habitats to live in on the long journey, shielding to protect from radiation, supersonic decelerators to descend through the Martian atmosphere, advanced life support for living on the surface, and much more. There will be a lot of that hardware, and some of it will be truly massive. And none of it does any good sitting on the surface of the Earth. If you want to get to Mars, you have to be able to put all of that into space. And that’s where Space Launch System comes in. You have to build a rocket. A big one.

An artist’s depiction of an astronaut and rover on Mars’ moon Phobos — A mission to one of Mars’ moons could potentially provide an opportunity for meaningful scientific work while the final Mars entry, descent and landing systems are still being completed.

And none of it matters unless you do it. Wernher von Braun went on Walt Disney’s Tomorrowland television program in the 1950s to talk about going to Mars, and much time has been spent talking about going to Mars in the decades since, by NASA, other countries, technical societies, industry, and others. You have to talk about Mars, you have to plan, before you can go, but talking and planning alone won’t get you there. You have to do something.

Today NASA is doing something in a way that neither we nor anyone have before. NASA’s Journey to Mars is unique in that it is the first and so far only time that any organization has actually begun building systems designed for human exploration of Mars. We have a long way to go, but we’re taking the first steps.

How do you get to Mars?

You build a rocket.

And go.

Next Time: Four Lessons In Four Years

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David Hitt works in the strategic communications office of NASA’s Space Launch System Program. He began working in NASA Education at Marshall Space Flight Center in 2002, and is the author of two books on spaceflight history.

Fourth and Very Very Very Long

A graphic showing that SLS would stretch almost from one end of a football field to the other — Comparing space to football is a grand tradition that may well have been started by John F. Kennedy himself, who compared going to the moon with Rice playing Texas in his ‘We Choose to Go to the Moon’ speech. If it’s good enough for JFK, it’s good enough for me.

Ah, September. That wonderful time of year when the air becomes cooler, leaves begin to turn color, and every discussion is required by law to include football metaphors. You certainly won’t see me intentionally grounding such a great opportunity, so let’s talk about what it means to “go long” in human spaceflight.

The first launch of SLS will send the Orion spacecraft into a large lunar orbit beyond the moon. But, really, how does that compare to previous human spaceflight missions? Let’s use a comparison to a football field to find out.

In real life, a football field, from the back end of one end zone to the other, is just slightly longer than the 322-feet-tall SLS. But for the sake of this metaphor, we’re going to scale the distance Orion will reach at its farthest point on Exploration Mission-1 to the length of that field. Imagine you’re standing at the very end of the end zone of an American football field. In the distance, at the far end of the other end zone, 120 yards away, is the farthest point Orion will reach on EM-1. Are you imagining it? Good.

First play, we’re tossing from the back edge of our end zone to the International Space Station. Complete! We’re well on our way! Well, sort of. This doesn’t quite get you out of your own end zone. In fact, at about 230 miles — roughly the driving distance between New York and Washington, DC — you’ve only gained about three and a half inches on our field.

A graphic showing the International Space Station near the end of a football field — The vast majority of time Americans have spent in space has been around the altitude of the International Space Station, but it’s just the beginning of this journey.

For second down, we’re going to be a bit more aggressive. Back in 1966, almost 50 years ago, two astronauts, Pete Conrad and Dick Gordon, set an Earth orbit altitude record of 854 miles on the Gemini 11 mission – the farthest humans have been without heading to the moon. But even when Gordon takes the ball, you’ve only covered a total of one foot.

Third down, aiming farther still. The altitude record reached on Gemini 11 is less than a third of the altitude Orion reached on its first spaceflight, Exploration Flight Test-1, in December 2014. Using that altitude, 3,600 miles, for our next play, we’ll be just over one percent of the way to our goal, at a total of four feet and eight inches from where we started.

It’s now fourth down, and we’re still at the back of our own end zone. For an even longer distance, we’ll use the distance the International Space Station travels during one orbit of the Earth – 26,250 miles. This play gives us our first down, and also put us out of the end zone by almost four feet.

A graphic showing a map of the Earth outside the end zone of a football field — Technically, orbital mechanics means that the physics of two Robonauts both in the same orbit around the Earth throwing a football any substantial distance between them wouldn’t actually be possible. (Besides, wouldn’t it have been easier to throw it the other direction?)

Sticking with Earth orbit distances is getting us nowhere. We’ve got to be even more aggressive. A long Hail Mary throw sends the ball to the far end of the field, where it’s caught … by Neil Armstrong on the moon! The crowd goes wild! TOUCHD… Wait… What? That’s still only at the other eight-yard line? Oh, well. Let’s keep going.

A graphic showing an Apollo astronaut catching a football near the opposite end zone of a football field — For the record, that picture’s not really Neil Armstrong. Also, the football wasn’t really in this picture.

You look toward the end zone, and there’s astronaut Jim Lovell of Apollo 13! He’s open, and you make the pass. On their emergency free-return trajectory around the moon on Apollo 13, Lovell, Fred Haise and Jack Swigert traveled farther from Earth than anyone has ever been, almost 249,000 miles out. But although Lovell went around the moon on two different Apollo missions, he was never able to touch down, and, unfortunately, he doesn’t now, either. Even the human distance record from Earth is short of the end zone, by three and a half yards.

Back in formation, the quarterback steps back, fires to Orion, caught in the very back of the end zone for a 23 and a half yard gain from where Lovell had it! TOUCHDOWN! On EM-1, Orion will travel about 10 percent farther into space than Apollo ever did. Not bad for a first test flight.

A graphic showing Orion at the opposite end zone of a football field — TOUCHDOWN ORION!

And, from there it gets interesting. Since this was just the first possession, you’d better not let that arm get tired – on our field, the trip to Mars will be about a 77,000 yard pass. Now, THAT is going long.

Next Time: The Journey to Mars

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The Engine Experience

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Can I make a confession? To be honest, I was a little bit jaded about going to see last week’s test firing of one of Space Launch System’s RS-25 engines.

Don’t get me wrong, when the opportunity to go came up, I took it in a heartbeat. I was even excited about it.

Let’s put this in perspective. I’ve seen shuttle launches. Not one, but three RS-25 engines, each time. Plus two solid rocket boosters. Stacked together, and heading into space atop a column of sky-splitting light and noise. If you never got to see one, they were pretty amazing.

So one RS-25? Going nowhere? Honestly?

A white cloud emerges from the A-1 engine test stand — With a history of almost 50 years, the A-1 stand was used for tests to make sure the Saturn V and space shuttle were ready for flight.

In case you missed it, in our last two blog posts, we talked about the test stand s and the engines themselves, and you can read about the 535-second test of the 12-million-horsepower engine and see video here.

But what was it like?

If some hypothetical foolish soul were to be naïve enough as to be jaded about an RS-25 test because they had seen shuttle launches, not that anyone would do that, it would be because they failed to appreciate two big differences in watching an engine test.

When you watch an engine test, you’re much closer to the action than you are for a shuttle launch. And the engine doesn’t go anywhere during the test.

The former fact means that you get a better sense of the details of what’s going on. Watching a launch, you see the shuttle rising atop a majestic plume of white. From a football field away, you see just how dynamic that white cloud is as it exits the engines, the speed and violence of the steam leaving the stand. You get a new appreciation of the power those engines are generating. You understand the volume of the engines in a new way as well. Out of curiosity, during the test, I loosened one of my earplugs ever so slightly, and quickly realized how dumb an idea that was. It’s loud. Like, really loud.

The fact that the engine doesn’t go anywhere means that you experience the entire burn. Watch a launch, and it’s ephemerally amazing and then gone. Watch an engine test, and it’s unrelenting. Power and sound washing over you for minute after long minute. More than one person commented to me about having a better sense of what was happening during a launch vehicle’s climb to orbit after witnessing the test.

David Hitt in front of RS-25 engine test — If you photograph a shuttle launch, you have your camera ready and snap as quick as you can. If you photograph a full-duration engine test, you shoot some video when it starts. Then take some pictures. Then watch for a while. Then switch cameras and take some more pictures. Then take a selfie. Then watch some more. Then get someone else to take pictures of you. Then take pictures of them. Then watch some more.

And then, at the end, a surprise I didn’t anticipate at all. In a launch, the end of an RS-25s burn comes in the silent void of space. On Earth, you hear everything. It’s hard to describe the sound that engine made as it ended the test – it reminded me of the astronaut descriptions of the shuttle I wrote about a few weeks ago. It was alive. A rolling growl of a mythic behemoth. Unearthly.

It’s been four years since I stood on a riverside in Titusville, Florida and watched the space shuttle Atlantis climb into the sky for the final time, and I still have years to wait until I watch the first SLS do the same.

To be sure, that future day seemed closer as I watched the RS-25 engine burn for a duration that would have put a spacecraft into orbit. Spaceflight is about speed, and speed is about power. The difference between being on the ground and being in orbit is less about altitude than it is velocity. Push something to 17,500 miles per hour, and it will orbit. Push it harder and faster, and it will go farther. This year, we’ve fired Space Launch System’s engines and boosters and demonstrated that right now we have the power we need to generate the speed. The next trick is completing the capability to keep those very thirsty engines fueled.

But I also came away from the test with a new appreciation for this time we’re in today, between those two launches. When I watched a shuttle launch, I didn’t have any sense of what one RS-25 engine was doing. I couldn’t distinguish it from the rest of the vehicle. Watching the test, you appreciate that engine. The power, the volume, the force of one RS-25. It’s an amazing piece of machinery. People came away with an excitement for seeing the core stage green run test in two years, when four engines will be integrated into the stage and fired together. Understanding what one engine is like, there was an eagerness to see that quadrupled.

The B-2 test stand at Stennis Space Center — Work is taking place today to prepare for an even more impressive test firing in a couple of years, when a 200-foot-tall SLS core stage will be fitted with four RS-25 engines and then placed vertically into the towering B-2 test stand and fired.

In March, we test-fired one of SLS’ solid rocket boosters, and those who were there talk about a similar experience. You didn’t get a sense watching the shuttle of what one SRB was contributing. But take it off the stack and fire it on its own? One SLS booster burns with the equivalent force of seven RS-25s, so you can imagine it’s impressive in its own right.

And it’s not just the propulsion systems. I got to stand within feet of the stage adapter that mated Orion to the Delta IV Heavy rocket used for Exploration Flight Test-1 in December 2014, a twin of which will connect Orion to SLS on our first flight. Look at a picture of SLS, and you barely notice that adapter. Stand next to the thing, and it’s a substantial piece of hardware.

This current period we’re in is about construction, but for me, I love that it has the added benefit of being about deconstruction. About taking one of the most amazing vehicles our species has created, and breaking it down to its parts. About seeing how incredible each of those parts is individually, understanding them better in their own right. About adding and understanding new parts, bigger and more advanced. And then, ultimately, taking those parts and putting them together in a new way to do a new thing.

So, yes, despite my naïve jadedness, I enjoyed watching the test firing. Immensely.

But, wow, am I looking forward to that launch.

Next Time: Exploration Football

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RS-25 Engines: Meeting the Need for Speed

Guest blogger Martin Burkey, the SLS strategic communications team’s resident expert on all things engines, returns this week as we prepare for this afternoon’s RS-25 engine testing event at Stennis Space Center – if you’re not already, follow @NASA_SLS on Twitter and our Facebook link below for more info. — David

Rocket engines are among the most amazing machines ever invented. That’s mainly because they have to do one of the most extreme jobs ever conceived – spaceflight – starting with escaping Earth’s deep gravity well. Orbital velocity, just for starters, is over 17,000 mph, and that only gets you a couple hundred miles off the surface. Going farther requires going faster. Much faster.

The RS-25 makes a modern race car or jet engine look like a wind-up toy.

It has to handle temperatures as low as minus 400 degrees where the propellants enter the engine and as high as 6,000 degrees as the exhaust exits the combustion chamber where the propellants are burned.

It has to move a lot of propellants to generate a lot of energy. At the rate the four SLS core stage engines consume propellants, they could drain a family swimming pool in 1 minute.

Graphic showing top speeds for an Indy car and SLS of 230 mph and 22,653, respectively — To be fair, the Indy car probably handles better in the turns.

The most complex part of the engine is its four turbopumps which are responsible for accelerating fuel and oxidizer to those insanely high flow rates. The high pressure fuel turbopump main shaft rotates at 37,000 rpms compared to about 3,000 rpm for a car engine at 60 mph.

The bottom line is that the RS-25 produces 512,000 pounds of thrust. That’s more than 12 million horsepower. That’s enough to push 10 giant aircraft carriers around the ocean at nearly 25 mph.

If the performance requirement to turn massive amounts of fuel into massive amounts of fire wasn’t enough, an engine can’t take up a lot of mass or area in a rocket. A car engine generates about half a single horsepower to each pound of engine weight. The RS-25 high pressure fuel turbopump generates 100 horsepower for each pound of its weight.

But forget mere car engines. The RS-25 is about the same weight and size as two F-15 jet fighter engines, yet it produces 8 times more thrust. A single turbine blade the size of a quarter – and the exact number and configuration inside the pump is now considered sensitive – produces more equivalent horsepower than a Corvette ZR1 engine.

Expanded view of an RS-25 engine — And this is still only the major components of an RS-25 engine.

On the other hand, when you chug fluids that fast, a hiccup is a bad thing. In the case of a rocket engine, that hiccup is called cavitation. At the least, it robs the engine of power. At worst, it can cause catastrophic overheating and overspeeding. So rocket engineers spend a lot of time making sure fluids flow straight and smooth.

That’s also why they test rocket engines on the ground under highly instrumented and controlled conditions. It’s a lot less costly to fail on the ground than in flight with a full rocket carrying people on board and/or a one-of-a-kind multi-million- or multi-billion-dollar payload.

As rocket engines go, the RS-25 may be the most advanced, operating at higher temperatures, pressures, and speeds than most any other engine. The advantage comes down to being able to launch more useful payload into space with less devoted to the rocket structure and its propellants.

In addition to its power, another key consideration for SLS was the availability of 16 flight engines and two ground test engines from the shuttle program. It’s much harder and more expensive to develop a new engine from scratch. Using a high-performance engine that already existed gave NASA a considerable boost in developing its next rocket for space exploration.

Top of an RS-25 engine during a test firing — The RS-25 handles a wide range of temperatures – super-cold on top, super-hot at the bottom.

The remaining shuttle engine inventory will be enough for the first four SLS flights. As for the maturity part, the RS-25 design dates to the 1970s and the start of the Space Shuttle Program. But it’s undergone five major upgrades since then to improve performance, reliability, and safety. If only we could all upgrade 5 times as we age. Further, much of the knowledge and infrastructure needed to use the available engines and restart production already existed. Another hidden savings in time and money.

In its next evolution, the RS-25 design will be changed to make it a more affordable engine designed for just one flight and certify it to even higher thrust – which it is very capable of – to make SLS an even more impressive launch vehicle.

Next Time: The Engine Experience

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How Is A Test Stand Like A Space Ship?

I’d like to introduce a special guest blogger this week, Martin Burkey. Martin is the SLS strategic communication team’s resident expert on all things engines. As we prepare for next week’s RS-25 engine testing event at Stennis Space Center – if you’re not already, follow @NASA_SLS on Twitter and our Facebook link below for more info – Martin will be filling in this week and next to talk about our engines and how we test them. — David

None of the test stands at NASA’s Stennis Space Center look anything like a spaceship. But they operate a lot like a spaceship, even though none of them will ever leave the ground.

A test stand is designed to make a fire-breathing rocket engine think it’s a spaceship, while at the same time keeping it from taking off for space the way it was made to. Those two requirements account for why test stands look and operate as they do… and why they aren’t as compact, light and sleek as a rocket.

Fire streaming from a test stand during an RS-25 test — Burning of the liquid hydrogen and liquid oxygen during an RS-25 test can actually cause the formation of rain clouds.

Most of the big Stennis test stands were built in the 1960s to test Saturn rocket engines. Over the years, they’ve continued to serve the nation by testing Space Shuttle Main Engines and other government and commercial rocket engines. Today, the center is buzzing with test activities in support of NASA’s Space Launch System.

The A-1 Test Stand is the focus of testing to adapt the RS-25 –formerly known as the shuttle main engine – to new SLS performance requirements and environments. It will also be used to test engines with new components for the second SLS mission. The B-2 Test Stand is being readied to support testing of the massive 200-foot SLS core stage with its four RS-25 engines.

Thousands of tons of hulking, ungainly concrete and steel hundreds of feet above and dozens of feet below the Mississippi soil keep the engine locked in place for testing under way this year. An intricate network of tanks, pipes, cables and other equipment provides the engine with all the propellants, power, pressure, vacuum, fluids, cooling, data management and other services to – safely and accurately – simulate a full rocket mission from pre-launch preparations to nearly 200 miles in space.

A worker inspects the machinery of an RS-25 engine — A test stands interface with the engine mimics the interface between the engine and an actual launch vehicle.

Why test the RS-25, an engine that flew successfully for more than 3 decades and has over a million seconds of operating time? Because the RS-25 is a complex and finely tuned piece of equipment that requires thorough understanding various component interactions and responses under different conditions. Like other rocket engines, it operates at extremes of temperature, pressure, vibration, etc. that have to be monitored. More specifically, the RS-25 needs to be adapted to SLS requirements and environments such as higher propellant inlet pressure and lower temperature and integrates technology like a new engine controller unit. The test stand environment allows controlled testing of abnormal conditions and more thorough monitoring and observation than the flight environment. Ultimately, it’s better to find problems on the ground than in flight. There’s a saying in rocket testing – “Test like you fly, and fly like you test.” In other words, make the engine do everything on the ground it’s going to have to do in flight, and don’t do anything in flight you haven’t made the engine do on the ground. Why are we testing a proven engine? Because Space Launch System is going to make its RS-25s do new things in flight, but not until every one of them has been done successfully on the ground.

The A-1 stand supporting the current test series provides the RS-25 with liquid hydrogen (LH₂) and oxygen (LOX) propellants. The stand has its own run tanks for propellants but they can also be filled from a 12-inch line running from LOX and LH barges docked near the test stand during test firing. The B test complex is also served by propellant barges, though stage testing relies on the propellant in the stage alone.

Aerial view of the test area at NASA’s Stennis Space Center.

From a safe distance, the Stennis test stands look like crude, utilitarian structures. Up close, they are intricately woven with a network of pipes, cables, and other hardware designed to exercise rocket engines and extract the important data.

The stand provides various gases such as nitrogen and helium for drying, pressurizing and preventing premature combustion in the engine, as well as breathing air for crews working in the engine nozzle before and after testing.

The stand also provides hydraulic and pneumatic pressure to operate the engine propellant valves. There’s electrical power to run the engine controller. There are data cables that carry engine performance information to and from the engine and the vehicle computers and crew. The high speed data system has 186 channels that can record various conditions at more than 100,000 times per second. Four high-speed cameras can record 250 frames per second. Low-speed video includes infrared, black and white and color cameras.

And, of course, there’s water for fire suppression on the stand and water to cool the stand’s ubiquitous “flame bucket” that directs engine exhaust exiting the nozzle at thousands of degrees away from the stand where it rapidly condenses into steam and then into rain that falls downwind. The A-1 bucket consists of 21 slanted deflector segments that make up the deflector seen in pictures. Each segment gets pressurized water, and each segment is drilled with a specific number and pattern of holes that spray water and keep the deflector cool during test firing. During tests, the stand uses 170,000 gallons of water per minute from a nearby reservoir.

The “crew” of the A-1 stand consists of about 50 people, some on the stand until 30 minutes before a test and others in the hardened Test Control Center 200 yards away from the test stand.

So while rocket engine testing may not resemble any real or fictional spaceship, it’s still very much “rocket science” and a critical part of getting NASA’s next great exploration rocket to the launch pad.

Next Time: RS-25 Engines: Meeting the Need for Speed

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Just What Is An SLS, Anyway?

For those lucky enough to be at or near Kennedy Space Center when a Space Launch System rocket leaves Earth for the first time, it will be an unforgettable experience.

Any rocket launch is amazing to witness in person, but the rise of a truly powerful launch vehicle, like the space shuttle or the Saturn V, is a different thing altogether. It’s not merely impressive; it’s visceral. It’s not something you witness; it’s something you experience, a brightness that seems like the sky has split open, a sound that you hear with your entire body, a power that passes into and through you.

Artist’s concept of SLS with vehicle elements pointed out — The first SLS will push off the launch pad with more force than either the Saturn rockets are space shuttle.

And for all the reasons that shuttle and Saturn V launches were in a different class, that first launch of SLS will be unprecedented; the power emanating from the vehicle, through the air and ground and into its audience measurably greater than either of those forbearers.

That unparalleled power will initiate an unparalleled mission – propelling the Orion spacecraft behind the moon, farther than any Apollo capsule ever ventured, proving that the system is ready to allow human beings to once more travel beyond low Earth orbit for the first time in decades.

That rocket, the first flight unit to come off the line, is already under construction. Today, large portions of that very vehicle can be found at NASA locations in three states.

At Stennis Space Center in southwest Mississippi, engines for that first flight, and the next three after it, are already in inventory. The RS-25 engines were formerly better known as the Space Shuttle Main Engine, and at the end of the shuttle program, 16 of its engines were transferred to the SLS program. While the shuttle used three of the engines per flight, SLS will use four; one of the ways the rocket is generating greater power than shuttle. Engine tests are being conducted now to check out improvements made to the engines since they last flew.

RS-25 engine undergoing testing — Engines on the shuttle ran at 491,000 pounds of thrust in vacuum (104.5-percent of rated power level). After analyzing temperature and other factors on the engine, the power level was increased for SLS to 512,000 pounds vacuum thrust (109 percent of rated power level).

At Michoud Assembly Facility outside New Orleans, the core stage of the first vehicle is being built. At one point, Michoud covered more square footage than any building in the country – 43 acres under one roof – and today large rooms are filled with rocket hardware. Barrels, rings and domes, 27.6 feet across, are coming off of welding machines and being stored awaiting the day they will be assembled together into fuel tanks. (For the test articles, that day will be this fall.) The SLS core will be the world’s largest rocket stage, and standing in front of those welded segments gives you a sense of just how big that is.

Four SLS barrel sections in a large room at Michoud Assembly Facility — In this picture, you can see four of the 27.6-foot-diameter barrels for the SLS core stage. Imagine taking those four barrels and stacking them on top of each other. That’s still only about two-thirds the height of the core stage hydrogen tank. Which, in turn, is less than two-thirds the height of the entire core stage. Which, in turn, is less than two-thirds the height of the entire rocket. See? You start to get a sense of how big this thing is.

At Kennedy Space Center in Florida, a large warehouse holds booster hardware for the first flight. As with the engines, the boosters for the first SLS flights are being repurposed and upgraded from the space shuttle program. The large white solid rocket boosters on the sides of the shuttle were actually a stack of multiple segments, with the four in the middle holding the propellant. The SLS boosters will be stacked with five propellant segments, also giving the rocket more power.

People look at a variety of booster segments in a large room — Pictured here is 3.6 million pounds of thrust, some assembly required, at the Booster Fabrication Facility at Kennedy Space Center.

Other elements of the vehicle are still yet to be built. The upper stage for the first vehicle will begin construction this summer at a United Launch Alliance facility in Decatur, Alabama. The upper stage is a modified version of the upper stage used on the Delta IV Heavy rocket that launched Orion on Exploration Flight Test-1 in December 2014. (Later flights will use a more powerful upper stage, just as the shuttle-derived boosters will eventually be replaced with more powerful boosters, making SLS more capability even than the Saturn V that carried men to the moon.)

At Marshall Space Flight Center in Huntsville, Alabama, two large adapters will be built; one to connect the core stage to the upper stage, and the other to connect the upper stage to Orion.

When all of these elements are completed, they will be transported to Kennedy Space Center for final assembly of the full rocket in the Vehicle Assembly Building. The entire SLS-Orion stack will tower 322 feet tall, and, when fueled, weigh more than five and a half million pounds.

At launch, the rocket will generate 8.4 million pounds of thrust, and have the power to launch more than 70 metric tons of payload into Earth orbit… or to send Orion farther into space than humans have ever ventured.

…And, of course, to give the Florida space coast a show like it’s never before seen.

Artist’s concept of the roll-out of the first SLS to the launch pad — The crawlers at Kennedy Space Center are no strangers to big rockets – they carried the Saturns and space shuttles to the launch pads since the 1960s. Even so, they had to be strengthened in preparation for transporting Space Launch System.

Next Time: Hey, How’s It Going?

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Designing A Rocket In Six Easy Steps

Let’s say you need to build a new rocket. Where do you start?

Well, what kind of rocket are you going to create? All rockets, after all, are not created equal – the world is full of a variety of rockets, all designed for different purposes.

Step One: Know What Your Rocket Needs to Do.
In order to know what kind of rocket you’re going to build, you need to know its requirements.

For the sake of this hypothetical example, let’s say the new rocket you need to build is to be designed for the purpose of human exploration of deep space. Specifically, it’s going to be the rocket that will enable human missions to Mars, far and away the most ambitious task ever undertaken in spaceflight history. A bold mission requires a bold rocket.

Blueprint-style drawing of the outer mold line of SLS — Blueprint of everything you need to build your own SLS, except for all the inner working that actually make it fly.

Step Two: Establish Mission Parameters.
Over history, there have been numerous studies of how to get to Mars, so you take the best data you can get and figure out what it takes to execute those missions. The general thinking is that you’re going to need multiple launches to carry out the mission, but even with multiple launches, there are going to be some really big pieces. You’re going to have to be able to lift at least 130 metric tons of stuff (a.k.a. payload) into Earth orbit. Many engineers think your lander may measure up to 30 feet across, so you need a payload volume big enough to carry it.

Step Three: Call in Experts.
You work with other rocket designers, in both the government and commercial spaceflight worlds. You listen to a lot of ideas. And I mean, a LOT of ideas.

Step Four: Start Drawing.
You start creating rocket designs. You work from a blank sheet of paper. In fact, you get a lot of blank sheets of paper. Reams of paper, really.

Step Five: Whittle Down the Possibilities.
The challenge, it turns out, is not to design a rocket capable of supporting human missions to Mars. The challenge is designing the BEST rocket for the mission.

And the real challenge of doing that is knowing which rocket is best. What’s the standard for “bestness” in a Mars rocket? It’s a more complex question than it might sound – it’s vital, for example, that the rocket be powerful, but the best rocket is not the one that’s most powerful. Once you have enough power, more power makes less difference.

As you probably guessed, this question is not completely hypothetical; four years ago, this exact scenario led to the birth of Space Launch System. Engineers were tasked with designing the 130-metric-ton Mars rocket described above. They called in government and industry experts. They reviewed more than 1,000 possible designs for the vehicle.

Small images of rocket design concepts — A selection of just a few of the major designs considered in early SLS studies. This graphic became known amongst the team as the “bedsheet” graphic, because, well, it would make an awesome sheet for a kid’s bed.

In the case of the SLS, some concepts were easy to reject: there were clearly better choices, for example, than the rocket that was too wide to fit out of the giant doors of the Vehicle Assembly Building at Kennedy Space Center.

Three stood out – a Saturn-like large, multi-stage rocket, using the kerosene fuel that powered the moon rocket instead of the shuttle’s liquid hydrogen; a rocket built from components based on current smaller rockets, taking advantage of industry successes; and a design that would be an evolutionary step from systems used on the space shuttle. But which was best?

External constraints had to be considered – in addition to the guideline that the rocket had to support human deep space exploration, national policy said it had to use, where possible, resources from the then-about-to-end shuttle program and earlier Constellation development effort. Any of the designs could have met this guideline; NASA worked to pick the design, and then identify existing resources that could facilitate its development.

NASA chose three additional standards to measure the rockets – any qualified design would be judged by how well it met standards of safety, affordability and sustainability.

Each of the three had strengths and weaknesses; engineers studied and debated the pros and cons of each. Ultimately, while the Saturn-like rocket was a good design, the time and cost needed to design, build, and launch it was too great. The smaller-rocket-derived design, in contrast, offered development advantages over the kerosene vehicle since the existing hardware and support systems provided a head start, but its complexity counted against it in the safety measurement. If you don’t have a barge, you can get the same effect by strapping a whole lot of rowboats together, but it’s not going to be the same.

The remaining design, based on a combination of upgrades to shuttle systems and new developments, provided advantages in shortening development time and reducing costs, and offering safety advantages through the use of proven propulsion systems.

Step Six: Pick the Best Design.
And so from the thousands, one remained — the design that could not only carry out the mission to Mars, but could do so most safely, affordably and sustainably.

The lengthy journey to the launch pad had begun.

Next Time: Just What Is An SLS, Anyway?

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Welcome to Rocketology

Someday, the story will be told of humanity’s greatest endeavor, the bold stretch across the harsh void of space to reach for another world, of how brave explorers set sail through a perilous nothingness armed only with their wits and the best vehicles and systems with which modern engineering could provide them, until they passed through the unwelcoming atmosphere of an inhospitable world millions of miles away and finally set foot in the dusty, rusty regolith of the Red Planet.

This blog is not that story.

This blog is the prologue to that story.

When you watch a space story, it usually starts with the rocket already on the launchpad, or the starship already in port. It doesn’t matter how it got there, it just matters that it’s there. Rarely do you see the movie that tells who built Columbus’ ships, who forged Excalibur, who installed Captain Kirk’s chair on the bridge of the Enterprise, who bolted together the rocket that carried Neil Armstrong to the moon.

This blog is that story.

Artist concept of the launch of a Block 1 SLS — Leaving the launch pad, SLS will generate more thrust than the space shuttle or the Saturn V!

NASA has begun the Journey to Mars, an integrated approach to exploration that will result in human landings on the Red Planet. The Journey will require much of the best of what NASA does – from robotic rovers sending back scientific data to astronauts on the International Space Station studying how long stays in space affect the body to engineers developing cutting edge technology to overcome currently impossible challenges.

A foundational capability in the Journey will be the Space Launch System, NASA’s new rocket that will be the most powerful launch vehicle in history, designed from the ground up to meet the challenges of human exploration of deep space. Sending astronauts to Mars will require massive new exploration systems, and SLS will be the rocket that will send them into deep space.

Artwork depicting an astronaut helmet, a bootprint on Mars, and a rover driving on the surface of Mars — NASA’s Journey to Mars, coming soon to a planet near you!

Like the Journey to Mars, SLS is built on NASA’s best, combining America’s past successes with state-of-the-art developments. SLS will give new life – and new upgrades – to the proven engines and boosters that powered the space shuttle, combining them with the largest rocket stage in the world. And that’s just the beginning; future upgrades will make SLS even more powerful.

With this blog, we’ll be giving you the story of the SLS rocket before it reaches the launch pad – a rare, once-in-a-generation behind-the-scenes look at how NASA designs, builds and tests a massive launch vehicle like none other in the world. We’ll be pulling back the curtain on the real-world “rocket science” – and rocket scientists – that will make possible the first footsteps on another planet.

David Hitt with a model of the Space Launch System rocket — David Hitt

Your docent for this tour will be David Hitt. I work in the strategic communications office of Space Launch System, helping to tell the story of NASA’s next great rocket. I first began working at NASA’s Marshall Space Flight Center in 2002 in education. I have a passion for history, and for NASA’s history – as a hobby, I’ve written two books on the subject – and so I’m fascinated by the opportunity to be witness to the unfolding of the next incredible chapter of that history.

The Journey to Mars has begun. Thank you for joining us on the journey.

Next Time: Building A Rocket In Six Easy Steps

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