NASA has said one of the strengths of its Space Launch System rocket is that the massive booster uses partially obsolete hardware. These proven technologies, such as the space shuttle’s main engines and side-mounted rocket boosters, give the agency confidence that the SLS will be reliable when it finally flies.
However, one problem with older hardware, built by traditional contractors like Orbital ATK and Aerojet Rocketdyne, is that it’s expensive. And while NASA hasn’t released per-flight estimates of the cost of the single-use SLS rocket, conservative estimates put it at $1.5 to $2.5 billion per launch. The cost is so high that it effectively rules out more than one to two SLS launches per year.
The space agency recognizes this problem with its rocket and has asked in the past for ideas on how best to reduce production and operational costs for its SLS rocket. Now the agency appears to be actively considering alternative hardware, including using potentially cheaper engines from a new space rocket company, Blue Origin.
Reconnaissance upper stage
The SLS rocket consists of side boosters to launch the launch pad and a core stage to launch the system into orbit. It will also have an upper stage to push the rocket’s payload out of low Earth orbit to its final destination, whether it be the moon, Mars or one of Jupiter’s moons, Europa.
For its first launch, likely in 2020, the SLS rocket will use a makeshift upper stage. However, NASA is developing an “Exploration Upper Stage” to give future variants of the SLS more lift capacity, and this new upper stage will debut on the rocket’s second flight, which could be in 2023 or 2024. four RL-10 engines, which have a long, proud legacy since their first flight in 1961.
But these engines, manufactured by Aerojet Rocketdyne, are also costly. (Ars understands that NASA paid an average of $17 million for each RL-10 engine for the first Exploration Upper Stage vehicle). So in October, to power the EUS, the space agency made a request to the aerospace community for “an inexpensive drop-in replacement engine to minimize program costs.” According to the document, the first set of four engines would be needed by mid-2023 in preparation for the third flight of the SLS rocket, known as Exploration Mission-3.
Then, after extending the deadline for responses beyond mid-November, NASA revised the RFI on December 1. The revised document no longer seeks a “drop-in replacement” for the RL-10 engine, instead calling for a “low-cost replacement engine.” While this seems like a subtle change, sources within the aerospace industry Ars indicated that it is significant. According to NASA, it was done to increase the number of responses.
“The original RFI was issued as part of an effort to reduce costs and improve affordability of the Block 1B version of the Space Launch System rocket and focused on the EUS engine itself,” a spokeswoman for the agency said. agency, Kathryn Hambleton, to Ars. “The revision looks at system-level performance to open up the field of possible responses while still ensuring compatibility with the EUS design.”
Opens the door to Blue Origin
The original wording of the RFI could be seen as a message of sorts to Aerojet, the engine manufacturer, that NASA expected to receive a discount on future RL-10 engines. However, by using “drop-in replacement” for a more generic replacement, NASA has indicated that it is now open to an architecture that uses fewer than four engines.
That would likely include Blue Origin’s BE-3U engine, which the company plans to use for the upper stage of the New Glenn heavy-lift missile. This is a modified version of the BE-3 engine that powers the New Shepard missile, which has now successfully flown seven times. Blue Origin previously marketed the BE-3U to Orbital ATK for its Next Generation Launch System, which is seeking an upper stage motor. A single BE-3U provides approximately 120,000 pounds of thrust, which is more than the 100,000 pounds of thrust provided by four RL-10 engines.
It’s not clear which companies responded to NASA’s RFI, which had a deadline of Friday, Dec. 15. However, this appears to be an attempt to provide the agency with options to improve the affordability and operation of SLS and to open the door to new technologies and new space companies for the massive rocket.