Full steam ahead for ATK’s SLS booster drive

by Chris Bergin

ATK are making good progress on both the initial five segment boosters, set to launch with the opening launches of the Space Launch System (SLS), and the Advanced Boosters that may provide yet more power to the Heavy Lift Launch Vehicle (HLV) in the late 2020s.


SLS Five Segment Booster:

Following the success of the three static fire tests of the five segment motor that was initially set to launch Ares I – before being re-purposed for the SLS – ATK are now deep into their preparations for the next major milestone, the Qualification Motor -1 (QM-1) test, which is set to take place at the end of this year.

The three Demonstration Motor (DM) firings provided a vast amount of data on the longer version of the booster that became famous during the Space Shuttle Program (SSP), with the most recent test – DM-3 – being the most heavily instrumented solid rocket motor in NASA history, with a total of 37 test objectives measured through more than 970 instruments.

The results of the DM tests have allowed ATK to complete the booster’s Preliminary Design Review (PDR) in conjunction with NASA, a milestone review that was conducted well within the planned schedule path for the opening SLS launch in 2017. The booster element for SLS currently enjoys around one year of margin.

The opening SLS mission, known as Exploration Mission -1 (EM-1), will involve two of the new five segment motors heading to the Kennedy Space Center (KSC) for Booster Integration (BI) processing, with the flow almost mirroring that used during the 30 year career of the Space Shuttle.

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“The booster PDR was successful and speaks to the importance of a collaborative design process with our NASA customer” noted Fred Brasfield, ATK vice president, Next-generation Booster.

ATK QM-1 Build UpWith the successful completion of PDR, the SLS booster team at ATK can now advance the design toward the Critical Design Review (CDR). This review will come after the next static fire involving QM-1.

Despite a slight slip in the schedule – mainly related to an issue with the aft segment of the QM-1, which was found to have about a two foot-wide area where propellant had debonded from the inside of the segment wall – the QM-1 segments are now building up at the test site at Promontory, Utah.

At present, engineers have both the forward and center segments being placed into position at the home of the booster test firings.

SLS Advanced Booster:

The five segment boosters will continue to provide the bulk of SLS’ launch power during first stage flight through into the second half of the 2020s.

Following that, SLS will receive an additional boost via the addition of “Advanced Boosters”, enabling SLS to evolve to a launch vehicle capable of lofting 130mT of payload – deemed a requirement for missions to Mars.

Liquid Advanced Booster, via L2Several companies are in the early stages of developing their proposals under NASA’s SLS Advanced Booster Engineering Demonstration and/or Risk Reduction (ABEDRR) procurement, ranging from solid to liquid options – such as Dynetics Inc./Pratt & Whitney Rocketdyne (PWR), who are proposing the use of the famous Saturn V F-1 engines to advance SLS’ capability to launch payloads of up to 150mT to orbit.

ATK’s own proposal – as outlined in a presentation acquired by L2 – builds on their legacy with the four and five segment boosters, with a motor that is “advanced” on several levels, by “provid(ing) NASA the capability for the SLS to achieve 130 mT payload with significant margin, utilizing a booster that is 40 percent less expensive and 24 percent more reliable than the current SLS booster.”

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Solid Advanced Booster, via L2The company’s proposal includes a higher ISP density of the propellent, boosting payload performance by nearly 25,000lbm, yet saving $9.2m in costs per booster. With the increased operating pressure, improved propellant, tailored thrust profile, increased expansion ratio all combine to provide a 15.1mT boost to the SLS’ payload capability.

Around six months into the development process, ATK’s Advanced Booster NASA Research Announcement (NRA) team is working to overcome key technological challenges and reduce the overall risk posture of an Advanced Booster.

According to ATK, some of the current Advanced Booster tasks are being worked on by the Propellant/Liner/Insulation (PLI) Integrated Product Team (IPT), who are tackling the challenge of developing a high-performance, low-cost PLI system.

ATK Advanced Booster Propellant MixingNot unlike testing different mixes of paint at a hardware store, the PLI IPT are busy establishing a design of experiments (DOE) matrix, cooking up 66 unique propellant mixes to test candidate propellant formulations for burn rate performance and mechanical property characteristics.

ATK note that several “families” of solid propellant formulations are being evaluated in the DOE, with multiple variations within these families undergoing testing to select the best formulation within each family to pursue further testing within larger scale mixes.

The team working on the mixes include expert propellant chemists Ingvar Wallace, Jay Shuler and Michael Smith, who are attempting to select the best mix by the early part of this summer, ahead of the favored propellant formulation being tested in the NRA’s 92-inch diameter integrated static test in early 2015.

Lead Image: Screenshot from the amazing 220mb super slow-mo DM-3 Five Seg Motor Ground Test Video –  available in L2 – LINK).

(Other Images: Via ATK, NASA and L2 content from L2’s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site.)

(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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