NASA's original ESAS focus was to enable both the ISS and lunar missions while enabling extensibility to Mars.
After further analysis, NASA has elected to alter the architectural baseline. The new approach places more emphasis on lunar missions sooner at lower overall risk and cost.
ESAS Update: Accelerating Lunar Missions
The ESAS was a 60 day study to establish a baseline exploration architecture
Intent was to use as a baseline from which to do further trade studies.
ESAS focus was to enable both the ISS and lunar missions while enabling extensibility to Mars.
After further analysis, NASA has elected to alter the architectural baseline.
New approach places more emphasis on lunar missions sooner at lower overall risk and cost, while
still meeting our commitments to the ISS.
Still employs a "1.5 launch" approach.
Still within the Constellation 5 year budget run out.
Will likely enable Mars missions earlier.
Crew Exploration Vehicle
ESAS baseline was to use LOx/Methane propulsion.
Initial studies indicated a performance advantage coupled with an ISRU strategy for Mars.
Common development for CEV, lunar ascent stage and Mars ascent/descent propulsion.
Significant risk, cost, schedule and technical driver. Reliability growth through multiple applications.
Mars mission ISRU strategy is very conceptual today
Don't want to over constrain the Mars architecture while increasing cost and risk to initial CEV deployment
After further analysis, it was determined that LOx/Methane has little if any benefit to the lunar architecture.
CEV and lunar ascent stage will not utilize LOx/Methane propulsion. Other state-of-the-art alternatives, including storable and non-toxic options will be evaluated. Still achieves reliability growth through multiple applications.
ESAS baseline required an unpressurized ISS cargo delivery vehicle.
A combination of planned ISS mission alternatives, design of the CEV service module, and the Commercial Orbital Transportation System (COTS) should provide NASA with the required capability without a dedicated development.
Initial ESAS assessments utilized a 5 segment RSRM with new liquid upper stage for the CLV
The five-segment development added significant near-term cost and risk and the J-2S/expander engine for the upper stage could not meet the 2011 schedule target."
Accelerating Lunar Missions (cont'd)
ESAS final recommendation:
CLV: 4 segment RSRM / 1 SSME upper stage (new SSME development for air start)
CaLV: 5 segment RSRM / 5 SSME expendable core stage (new SSME developed in 2 steps) / 1 J-2 EDS stage (new upper stage engine development).
Required development of two upperstage engines, a two step approach to a low cost SSME derivative and two solid booster stages.
Budget limitations forced NASA to slip the 1st CEV flight target to 2012, in addition to budget offsets from CEV design changes allowed NASA to reevaluate this recommendation.
The reevaluated cost and schedule to implement these changes will result in lower overall risk to the lunar mission, enabling the lunar missions sooner due to earlier development of the required hardware (fewer development steps/changes)
A 5 segment RSRM test motor was successfully ground fired in 2003 as a Shuttle margin test.
The J-2 engine successfully powered all Apollo/Saturn V missions (S-II & S-IVB stages).
A 1993 NASA funded study, updated under ESAS, laid out a plan for restarting production on the J-2S.
4 sets of J-2S Mk 29 turbopumps were successfully fabricated, integrated and tested in the X-33 main engine in the late 1990's.