by Douglas Messier
NASA has set mid-2022 for the second flight of the Space Launch System (SLS), but it’s not yet known what the massive booster will actually launch.
“Determination as to whether this launch will be SLS/Orion crewed mission (EM-2) or the SLS/Europa Clipper mission will be made based on risk and readiness of the Europa Clipper project,” according to a decision memo signed on Friday by William C. Hill, deputy associate administrator for Exploration Systems Development. Parabolic Arc obtained a copy of the memo.
EM-2 will be the first crewed flight of the Orion spacecraft. The mission will send up to four astronauts to the vicinity of the moon on a flight that will take them further out into space than the Apollo crews traveled.
The Europa Clipper orbiter will make the first detailed survey of Jupiter’s frozen moon, which scientists believe hides an ocean beneath its icy surface. The mission will be followed by an Europa lander, whose launch is currently scheduled for 2024.
Both EM-2 and the Europa Clipper missions will use the SLS Block 1 configuration, which is capable of lifting 70 tons into low Earth orbit (LEO). The flights will use Mobile Launcher 1 (ML-1) “with minor modifications to support crewed flight (update to caution and warning system, implementation of emergency egress system),” the memo stated.
“Maintenance of ML-1 in the SLS Block 1 configuration allows for the launch of the Europa Clipper science mission on Block 1 as early as the June 2022 planetary window,” the memo added. “Current analysis show sufficient Block 1 capability to support a direct trajectory of Europa Clipper to the Jovian system, without need of Earth or Venus flybys, through the available launch windows in the 2020s.”
The document cancels an earlier decision memo that directed the implementation of the larger SLS Block 1B capability for the EM-2 mission. “Mission objectives of EM-2 can be achieved using SLS Block 1 with the ML-1 in the current SLS Block-1 configuration,” the memo said.
The SLS Block 1B launcher will be capable of lifting 105 tons into LEO — a 50 percent increase over SLS Block 1. With the Orion crew vehicle, Block 1B will stand 364 feet (110.9 meters) tall – 42 feet (12.8 meters) taller than SLS Block 1.
NASA is constructing a second mobile launcher (ML-2) specifically designed to support the SLS Block 1B launcher and larger variants of the booster. “Planning should assume an SLS Block 1B launch using ML-2 in the first quarter of the calendar year 2024,” the memo stated.
ML-1 will be converted to support SLS Block 1B and later booster variants if funds become available.