NASA's Marshall Space Flight Center
intends to buy 18 additional RS-25 rocket engines from Aerojet Rocketdyne in Canoga Park, Calif., to support the agency's new Space
Launch System (SLS). The estimated value of this proposed action is
$2.2 billion with an estimated period of performance from date of
execution through July 15, 2028.
“RS-25” is the generic designation
for the staged combustion, liquid hydrogen/liquid oxygen rocket
engine system previously known as the Space Shuttle Main Engine
(SSME) and it is the established core stage engine for the new SLS
rocket. This proposed effort will be based on a previously existing
production line for an engine system with thirty years of human
spaceflight history. It is not a new engine development effort. The
purchase of 18 additional RS-25s will fullfill the SLS Program engine
requirements that are beyond the scope and the period of performance
of the current contract, which provides six RS-25 flights engines
with a period of performance through Sept. 30, 2024.
The new SLS vehicle uses a
“stage-and-a-half” configuration that ignites the four core stage
engines seconds before liftoff and then ignites the solid motors
(boosters) at liftoff. The boosters burn out approximately two
minutes into the flight while the core stage engines continue to burn
until the desired cutoff point is achieved. This basic configuration
is flexible for both early demonstration flights and for ultimately
evolving the SLS vehicle to a configuration with a capability to lift
130 metric tons to low-earth orbit in support of future exploration
missions.
NASA's strategy for minimizing the cost
for development of the new SLS vehicle is to leverage the assets,
capabilities and experience of the Space Shuttle Program. Early SLS
flights will utilize 16 RS-25 engines from the Space Shuttle Program
with necessary refurbishment and adaptations for SLS. The
availability of 16 flights assets was one factor in selecting the
RS-25 for the SLS architecture along with the demonstrated
performance and extensive experience with this engine. These 16
assests can be used for the first four flights of SLS, with four
engines per stage.
In addition to the 16 engines, six new
engines were previously procured under the current contract to
provide engines for the fifth SLS flight and two risk mitigation
spare engines.
For the additional 18 RS-25 engines, it
is estimated that each unit will take five years to fabricate and
assemble. While it will be the goal of this procurement action to
reduce this cycle time, the timeline of five years matches the
documents Aerojet Rocketdyne historical norm for this engine.
Aerojet Rocketdyne designed, developed,
and matured the RS-25 engine system as the SSME over the past
forty-plus years, and has been the only source utilized for the
design, development, manufacture, refurbishment, recycle, testing,
and flight operations of the RS-25 for the life of the Space Shuttle
Program. Further, Aerojet Rocketdyne is the contractor currently
responsible for adapting the residual Space Shuttle RS-25 hardware
for use as part of the SLS Program. No other contractor has this
accumulated knowledge with respect to hands-on technical experience
and programmatic history of this engine.
Aerojet Rocketdyne manufacturing is
performed at three facilities; machining, welding, assembly and test
of subassemblies at the Canoga Park California Strategic Fabrication
Center, turbopump assembly operations at the West Palm Beach, Florida
facility, and final assembly and test at the NASA Stennis Space
Center in Mississippi. While the NASA Stennis Space Center is a
Government-owned facility, the other two facilities are Aerojet
Rocketdyne facilities.
Aerojet Rocketdyne (and its predecessor
companies) is the only contractor in this country to design and build
large liquid hydrogen/liquid oxygen rocket engines for human
spaceflight. They designed and built the first liquid hydrogen/liquid
oxygen engines to ever fly, the RL10, first launched in 1963. They
designed and built the J-2 engine used for the second stage of the
Saturn IB vehicle and the second and third stage of the Saturn V
vehicle. Furthermore, they designed and built the world's largest
liquid hydrogen/liquid oxygen production engine, the RS-68, for the
Delta IV vehicle in support of the Department of Defense. And most
recently, they restarted production of six new RS-25 flight engines
for the SLS Program.
For the past forty-plus years the RS-25
was, and remains today, the highest performing large staged
combustion liquid hydrogen engine in the world. It is a unique engine
with unique capabilities that took substantial and prolonged effort
to develop and certify for human spaceflight. An attempt to develop a
new engine with a new contractor (or the RS-25 engine with a new
contractor) would require significantly more engine hot fire testing
to certify for flight.
The RS-25 engine design carries with it
four decades of development and production activity and three decades
of flight experience. As a staged-combustion liquid hydrogen engine,
the RS-25 engine design is also the most advanced and complex engine
ever built and flown. With over one million seconds of accumulated
hot-fire test time and the equivalent of over four hundred human
spaceflights, the RS-25 design, production processes, and operational
procedures have incorporated within them thousands of lessons
learned.
The overall period of performance for
the proposed activity in support of the current SLS Program flight
manifest is approximately nine years. To support an August 2025
launch of a fifth mission, the first four engines must be delivered
no later than July 2025. Based on historical data it takes a
lead-time of approximately five years to fabricate and assemble the
engine. Based on an ATP of July 2019, the first of four engines would
need to be delivered in July 2024. Assuming the engines are delivered
every three months, the fourth engine would be delivered in April
2025, with about three months contingency in the schedule. The last
of the 18 engines would deliver in the first quarter of fiscal year
2028.
