The Marshall Space Flight Center (MSFC) has issued a “Justification for Other Than Full and Open Competition (JOFOC)” solicitation in support of sole sourcing RL10 engines for the Exploration Upper Stage (EUS) from Aerojet Rocketdyne. The document calls for an initial order of 10 engines to cover the first two flights of the Space Launch System (SLS) with the powerful upper stage.



EUS:

The initial plan was to switch to this new upper stage after the crewed EM-2 mission. However, as previously reported by this site, NASA wishes to advance this plan.

The debut of SLS will be known as the “Block 1”, sporting a Delta Cryogenic Second Stage (DCSS), renamed the Interim Cryogenic Propulsion System (ICPS) for SLS. The original plan called for two DCSS orders (EM-1 and EM-2) before NASA placed a stop work order on the second unit.

As noted in numerous meetings – not least by NASA’s Aerospace Safety Advisory Panel (ASAP) – it would cost around $150m to “human rate” the DCSS ahead of EM-2, a cost that would be associated with just the single use of the stage ahead of moving to the EUS.

As such, the plan now involves with moving to the EUS as soon as possible, namely the second flight of SLS.

With SLS moving to the Block 1B configuration after the 2018 test flight, NASA will take advantage of the several year schedule gap between the first and second flight of SLS – a gap that may be as long as five years.

During the gap, the Mobile Launcher will require another revamp after the first flight, with the Fixed Service Structure (FSS) and umbilicals reworked to align with the taller Block 1B.

The effort to move to the EUS has been ongoing since 2013.

The SLS program completed the Systems Requirements Review (SRR) for the stage in January 2015, which set forth the Point Of Departure (POD) of the Block 1B configuration to be used starting with EM-2.

Per the EUS POD, the definitions called for the stage to utilize four RL-1OC-3 engines (EUSEs). However, other alternatives were still on the table as the effort moved from a trade study in 2013 and entered the POD phase a year later.

NASA received nine responses from eight different companies during a Request For Proposals (RFP) process. Three of the proposals entered the trade study, while the remaining proposals consisted of a mix of “conceptual” or “early development” expander cycle, staged combustion, and aerospike engines.

“These six proposals involved engines are a lower state of design maturity and thus would require unaffordable cost and schedule delays to mature and certify for the SLS Program,” the document noted.

It was also estimated that even the most optimistic development programs would delay SLS missions EM-2 by four years and EM-3 by two years in terms of providing ﬂight quality/certiﬁed engines, resulting in substantial additional program costs across SLS elements.

Further meetings focused only on the RL10, with that engine – in units of four per stage – now baselined.

The RL10 is an expander cycle liquid hydrogen/liquid oxygen rocket engine typically used on upper stage applications. It was ﬁrst developed by Pratt & Whitney in the late 1950s and ﬁrst ﬂown in 1963.

It has ﬂown on hundreds of launches, logged approximately 15,000 hot ﬁres, and accumulated more than 2.3 million seconds of hot ﬁre operation time with a demonstrated reliability ratio greater than 0.999 throughout its history.

The RL10 – which is used in various forms with Atlas’ Centaur Upper Stage (RL10A-4-2) and Delta IV’s Upper Stage (RL10B-2) – has a history back to the Saturn I’s S-IV Stage.

The RL10 also came “to the rescue” of the recent OA-6 Cygnus mission, when the Atlas V booster underperformed, requiring the RL10-powered Centaur to burn much longer than planned to loft Cygnus into a nominal orbit.

The JOFOC document is a requirement to cover the Federal Acquisition Regulation (FAR) element of moving forward with a sole source – namely Aerojet Rocketdyne – for the EUS engines, explaining why the program won’t be holding a competitive process.

“NASA MSFC proposes to issue a sole source contract to Aerojet Rocketdyne to procure ten RL10 ﬂight engines, vehicle and program integration, ﬂight support for Space Launch System (SLS) Exploration Missions (EM) 2 and 3, and human rating compliance review,” noted the document.

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“The SLS Program completed a detailed trade study in May 2014 that determined the appropriate engine(s) to be used in conjunction with the proposed Exploration Upper Stage (EUS), a liquid oxygen and liquid hydrogen upper stage.

“The results and recommendations of that study and the subsequent SLS Program direction are in alignment with regards to the steps necessary to support EUS design, development, test and evaluation (DDT&E), certiﬁcation, and ﬂight operations.”

In showing the program had adequately evaluated the alternatives, details of the 2014 trade study showed the decision checklist worked with the technical parameters in terms of thrust, speciﬁc impulse, physical envelope, propellant constituency and volume, stage cost (including engine development costs), stage reliability, and similar factors and constraints needed for the upper stage.

“The study’s engine choice was the dependent variable – that is, the SLS mission requirements, input variables, and constraints were analyzed and resulted in a set of performance parameters for the engine,” added the document.

“The resulting performance parameters and other NASA technical requirements best match those delivered by an RL10-class engine (24-35K thrust) in a cluster of four conﬁguration. Further, the trade study determined that a 4-engine cluster is optimal for vehicle loss of mission reliability.

The order of 10 engines (eight flight-assigned engines and two spares) has a cost figure, although that figure was redacted from the document.

The contract has an estimated period of performance from the date of execution through December 31, 2023 – although engine delivery is required two full years ahead of the expected launch dates.

NASA will also pay for program integration support from Aerojet Rocketdyne as part of the deal because “NASA has not designed a ﬂight stage using RL10 engines since the early 1960s (Saturn 1).”

The company will also help build data on the breadth of “human-rating” facets with this power unit.

The contract award – if fully completed – will also help grease the wheels in “accessing company limited rights or proprietary material and technical, programmatic, and historical knowledge of engine performance, functional, operational, and physical characteristics” of the engine.

As was noted with procurement of new expendable RS-25s as the preferred first stage engine for future of SLS, the document adds “it’s important to note that this proposed effort will be based on the existing production line for an engine system with 50 years of space ﬂight history and is not a new engine development effort.

“NASA studied and considered the option of developing a new engine design but determined that the cost, schedule, technical, and safety risks of that approach outweighed the potential beneﬁts for the EUS ﬂights. Based on that assessment, NASA requires the use of the RL10 engine system in support of the SLS EM-2 and EM-3 missions.”

Ironically, the document cites the cost of the since-cancelled J-2X development as a reason against a new engine development alternative to the RL10, claiming it would cost around $1.2 billion if such an effort required a new test stand.

It is also claimed such a path would require six to seven years of work, adding years of delays to SLS’ schedule. Even a new in-house engine development based on the RL10 wasn’t classed as viable based on the flight heritage of the current RL10.

“Given the technical and safety-related rationale for utilizing the mature RL10 design as the EUS engine, and considering the unique RLIO experience, knowledge, and capabilities possessed by Aerojet Rocketdyne, the RL10 engine is the only available source for the EUS engine.”

In conclusion, the document closes its argument by adding no responses were received from the industry as a result of the posted synopsis which closed in February.

Also, due to “the extensive, unique, proprietary, and historical knowledge and experience with Aerojet Rocketdyne, there are no speciﬁc actions that the Agency may take at this time to remove or overcome barriers to competition for the EUS engine.”

It ends by noting Aerojet Rocketdyne is in the only position to successfully provide the Government’s requirement – while citing the 2010 Authorization Act that leaned towards heritage hardware – for the SLS Program.

The company will now be tasked with submitting a full proposal that will be evaluated and negotiated by the Government while the EUS continues its design phase with the RL10s baselined.

Images: ULA, Aerojet Rocketdyne, DLR, NASA and L2 (All EUS graphics) – including renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)

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