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NASA building world's largest solid-fuel rocket


October 4, 2012

SLS solid rocket booster segment being moved (Image: ATK)

SLS solid rocket booster segment being moved (Image: ATK)

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When NASA’s Space Launch System (SLS) enters service in 2017, it will replace the historic Saturn V as the largest, most powerful space launch vehicle ever flown. To lift its initial 70-metric ton (77 ton) payload into orbit, the SLS will rely on additional boost from a pair of the largest solid rocket motors ever to be built for flight. The first of these boosters is being assembled for NASA in Brigham City, Utah by ATK Space Systems using new manufacturing methods intended to make these behemoths safer and less expensive.

When the SLS enters service in 2017, it will have ten percent more thrust than the Saturn V rocket at liftoff and is intended to launch the Orion manned spacecraft and for lifting large payloads for deep space missions such as a possible space outpost orbiting beyond the Moon. In addition to the four RS-25 former space shuttle main engines that will power the first stage, the SLS will also use two advanced solid rocket boosters.

These boosters are derived from the Space Shuttle boosters, though they are larger and of an improved design. Where the Shuttle boosters were made in four segments, the SLS boosters are made in five. These segments contain the fuel, which is composed of ammonium perchlorate, powdered aluminum, iron oxide, a polymer (such as Polybutadiene acrylonitrile (PBAN) or hydroxyl-terminated polybutadiene (HTPB)) and an epoxy curing agent. Like the Shuttle’s, the SLS boosters are reusable, though they are much more powerful. Where a shuttle booster put out 2.8 million pounds of thrust (12,000 kN), and SLS booster reaches 3.6 million pounds (16,000 kN).

The engine currently being assembled by ATK is called Qualification Motor-1. It’s not intended for flight, but rather as a test rocket to evaluate design and construction, with the first test firing scheduled for the spring of 2013. In manufacturing the booster, ATK cut costs by 46 percent by streamlining the assembly process and replacing x-ray inspections with an ultrasonic examination of the booster's nozzle. This allowed the tests to take place on the factory floor rather than moving the nozzle to a special location.

The basic idea was to provide a more hands-on approach toward assembly and inspection to keep an eye out for any flaws and to move the booster as little as possible during assembly. In one case, part of the assembly process that required 47 moves now only required seven. This greatly reduces the chances that the booster might be damaged during assembly.

This effort to avoid damaging the booster is more than just a cost-cutting exercise. It’s also a way of improving the safety of the booster. The solid rocket motor puts out extreme heat and pressure that must be kept contained and controlled. It was the failure of a simple rubber o-ring that turned one of the Challenger’s boosters from a rocket into a blowtorch that destroyed the spacecraft. In order to keep the SLS from going from the biggest rocket to a very big bomb requires a lot of care and a lot of attention to detail.

Source: NASA

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy

SLS/orion is pure pork payoff to the old school NASA contractors. Total waste of money. Kill this redundant pos now please.

Brian Mcc

This could do everything SLS could do and more..for less. And will fly next year.

Falcon Heavy..


Brian Mcc

I'm glad ATK was able to get this contract. ATK lost money (underbid) on their contract to build the sabilators for the F-22. I had the chance to do an ultrasonic inspection of some carbon fiber X brace panels while I worked there, it's great for showing delamination defects in composites. They did a great job with overhauling the Pegasus and other ICBM missiles; there truly aren't a lot of facilities with their capabilities.

Ali Kim

@ Brain Mc - I agree completely. HUGE waste of money that could be spent on much better space related things, like probes to Titan or Europa, or a million other destinations! NASA needs to gets it large bureaucratic ass out of the rocket building game.

Derek Howe

SLS "will replace the historic Saturn V as the largest, most powerful space launch vehicle ever flown." Energia (http://en.wikipedia.org/wiki/Energia) had more power then SLS (http://en.wikipedia.org/wiki/Space_Launch_System).


It's time for NASA to turn this well known tech over to the private sector. While we need gov to get things started, that was 60 yrs ago!!

Companies like SpaceX have proven they can for far less money do the jobs. Let's let them do it.

Other things like health care though business can't seem to handle gouging, bankrupting us so gov should step in there where Gov has proved in many countries they do better for 50% less cost.


SLS is not scheduled to enter service until 2019 or later. The 2017 flight would be an unmanned test flight, if it happens.

Jon A.

@ Misha - If this gets built (and I hope it doesn't) it would eventually be a largest rocket ever. The 70 metric ton is just one configuration, it will go as high has 130 metric tons. http://en.wikipedia.org/wiki/File:SLS_configurations.png

@ Brian - NASA is building a SUPER heavy, not just a heavy. So no, Space X's Falcon heavy couldn't lift near what NASA's SLS could. That said, Musk has talked about building a super heavy if the need was present. While I don't remember how much he said he thought he could build it for, one thing is clear, it would be FAAAAAAAR cheaper & quicker then NASA could build the equivalent for.

Space X is a phenomenal company. Not only are they cheaper then everyone else (per launch), but they push the boundaries of what is possible. NASA helped them get where they are, and soon NASA will be eating their dust. Which is great, NASA needs to focus on the science aspect, not building the rockets.

I hope all goes well on Falcon 9's sunday launch to the ISS!

Derek Howe

agree with jerryd, Privitize the SLS & move into deep space NASA. Pvt sector can do SLS better alone., & produce faster vs govt style in 60s era.

Stephen Russell

The components for a heavy lift rocket already exist, they've existed for over 30 years.

Take the external fuel tank used for the shuttle. Modify the design to place the three shuttle main engines under its bottom end. Modify the top end to support a payload with the mass of a loaded Shuttle.

Want to lift more? Change the tank design to accommodate four of the solid booster rockets.

Another idea would be to add two smaller solid rockets to boost the empty external tank into orbit. Early in the Shuttle program there were plans to orbit the tanks for use in building space stations. That got axed in favor of dropping them in the oceans. Such a waste of millions of dollars of material.

Most of the engineering and design work already done so the cost would be far less than developing a new rocket to do the same job.

Too obvious and would save too much money.

Gregg Eshelman

meanwhile at NASA: hey we have a reusable orbital launch vehicle. lets retire it and waste our massive budget on single use rockets!!!! great idea.


I agree that NASA, like our government, is very wasteful with money, they did manage to go to the moon when our nation's political pride was along for the ride, but they cannot get together to agree on a new shuttle design, so Burt Rutan did it for them and at a small fraction of the cost. . I approve of the new super heavy lift rocket for obvious reasons such as a newer, improved rocket motor design and the ability to put a whole new space ship in orbit or a bigger one in a few trips. I am all for more probes everywhere, but that isn't the long term goal. Manned exploration and possible terraforming is. I want to see NASA get off their collective butts and get something big done and leave the smaller stuff to the private sector. They have a huge budget, I want to see huge results, not just a lot of little probes everywhere. I want to see a refuelable space ship in orbit ready to take off anywhere we want to go. I want to see nuclear engines.

Ronald Cooper

@Gregg, I don't know if you're being facetious or not, but that is exactly what they've built with the SLS... it's mostly modified shuttle stack components.


re; Ronald Wade Cooper

Nuclear engines can produce high thrust levels more efficiently than chemical powered engines but do not provide the power to lift vertically from the ground but it could power a winged craft's horizontal launch and if you use the engine's reactor properly you could use propellers/ducted fan or atomic jets for take off and save your stored reaction mass for high altitude/orbital insertion flight.

The nuclear engine that can be used to land and launch on the moon is not the best engine to power the transition from LEO to Lunar Orbit. the ion engine that is best for the orbital transfer does not produce enough thrust for the lunar landing and launch but the nuclear reactor powering the nuclear rocket could also be used to provide the power to operate the ion engine used for deep space work.

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