After years of speculation, NASA officially announced Friday that SpaceX’s Falcon Heavy would launch what is arguably the space agency’s most important Solar System exploration mission of the 2020s—the Europa Clipper.

Slated to launch in October 2024, the $4.25 billion mission will spend much of the remainder of this decade flying to the Jovian system before entering an elongated orbit around Jupiter. The spacecraft will then make as many as 44 flybys of Europa, the intriguing, ice-encrusted Jovian moon that scientists believe harbors a vast ocean beneath the surface. It is possible that aquatic life exists there.

The total contract award amount for launch services is approximately $178 million, NASA said in a news release. This is a significant moment for SpaceX, as the company will be entrusted with one of NASA’s highest-priority exploration missions. The deal also saves NASA about $2 billion.

The selection of a launch vehicle for this ambitious mission has been subjected to a long, drawn-out political process. Originally, at the urging of Congress, NASA planned to launch the spacecraft on its Space Launch System rocket. There were two reasons for this. Legislators (particularly US Sen. Richard Shelby, R-Ala.) wanted to find additional missions for the SLS rocket. And second, the powerful SLS rocket had the ability to get the Clipper to Jupiter within about four years.

However, many in the scientific community preferred to launch on SpaceX’s Falcon Heavy for a variety of reasons. For one, SpaceX offered launch services at a steep discount compared to the SLS rocket, which the White House estimated would cost more than $2 billion for the Clipper mission. Scientists were also concerned that the oft-delayed SLS rocket would simply not be ready for a 2024 launch date, and selecting it would delay the science mission.

However, politicians continued to insist that NASA launch Clipper on the SLS rocket. Three different events finally forced legislators to relent. First, in late 2018, NASA scientists concluded that the Falcon Heavy could complete the Clipper mission without needing a gravity assist from Venus, and therefore it would not have to go into the inner Solar System. The Falcon Heavy could do so with the addition of a Star 48 “kick stage.” (United Launch Alliance’s Delta IV Heavy rocket would have necessitated a Venus flyby, significantly increasing the thermal shielding needed on the Clipper spacecraft, so it was eventually ruled out.)

“Nobody is saying we’re not going on the SLS,” Barry Goldstein, of NASA, said at a meeting in November 2018. “But if by chance we don’t, we don’t have the challenge of the inner Solar System. This was a major development. This was a big deal for us.”

Second, after finalizing plans for the Artemis Moon Program, NASA realized that the primary contractor for the SLS rocket’s core stage, Boeing, simply was not up to the task of building an additional rocket for the Clipper mission in time. All of the SLS core stages, NASA officials realized, would be needed to support the effort to land humans on the Moon in the mid-2020s.

Finally, what forced Shelby and the rest of Congress to give in was a “shaking” issue with the SLS rocket. This large vehicle is powered off the pad by two very large solid rocket boosters that produce significant vibrations. SLS program officials had been telling the agency’s leadership that the torsional load—essentially a measurement of twisting and vibration—was a certain value. However, after NASA performed wind-tunnel testing, the actual torsional load value was nearly double the SLS program estimates.

Accommodating for this launch stress, NASA officials told Ars, would have required an additional $1 billion in modifications to make the spacecraft more robust. That additional cost was ultimately what led NASA to be able to make Friday’s announcement.

Listing image by Trevor Mahlmann

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