The Hill's NASA's Europa Clipper has been liberated from the Space Launch System is quite an illuminating read about the politics of space launch. However, I noticed that it also says:

Both the economics and physics of getting to Europa change if SpaceX’s Starship, currently under development in Boca Chica, Texas, becomes available to launch the Europa Clipper in the mid-2020s. The Starship is meant to fulfill SpaceX’s CEO Elon Musk’s dreams of settling Mars. But the massive reusable rocket would be available for other things, presumably including sending probes to the outer planets.

The massive cost savings by using a commercial launcher for the Europa Clipper creates other possibilities. The Europa Lander could be placed back on. A mission to Saturn’s frozen world Enceladus may also be greenlit.

Question: In what ways would the "physics" of getting the Clipper to Europa change if Starship was used instead of SLS? Are the orbital mechanics of interplanetary flight changed? Number of stages or number of flybys different?

It's certainly quite a delta-v challenge to get from Earth to Jupiter and then deep enough down in Jupiter's gravitational well to match Europa's orbit and then land safely on its surface without any atmosphere on the moon for aerobraking. But how would Starship and SLS solutions differ?

  • 2
    $\begingroup$ Musk's supernatural mojo transcends physics? $\endgroup$ Commented Jan 11, 2021 at 3:04
  • 1
    $\begingroup$ @OrganicMarble perhaps Boring Company will tunnel through spacetime to Europa and the Clipper will be towed by a Cybertruck $\endgroup$
    – uhoh
    Commented Jan 11, 2021 at 3:12
  • $\begingroup$ @uhoh I'm getting Peter F. Hamilton vibes from that. Compression Space Transport anyone? $\endgroup$
    – BMF
    Commented Mar 7, 2021 at 5:17

2 Answers 2


The big difference is that Starship is intended to be reusable and is expected to come back to Earth, though expendable options have been discussed. SLS or Falcon Heavy would launch a probe like Europa Clipper directly to an interplanetary trajectory, along with a kick stage in Falcon Heavy's case. The upper stage of the launch vehicle would end up abandoned in solar orbit.

There's multiple ways to do it with Starship, but most likely it would instead deploy Europa Clipper and a larger kick/departure stage into LEO. It might take on propellant in orbit and deploy them to a higher energy orbit to give them a bit more boost. In an extreme case, it might launch into a solar orbit that brings the Starship back to Earth in a couple years. The expendable option would do something similar, just without the eventual return to Earth.

Given the ample payload capacity, the first option which only requires a larger departure stage would seem the most likely. The other options would come into play if you can no longer fit the probe and its departure stage into a Starship, which would be something a bit beyond the scope of a Europa Clipper scale mission.

  • $\begingroup$ Can you highlight which parts of your answer address specifically the "physics of getting (Clipper) to Europa"? This is mostly about getting Starship back to Earth. Thanks! $\endgroup$
    – uhoh
    Commented Mar 7, 2021 at 2:30
  • $\begingroup$ That would be because the main ways the physics differ result from the fact that the Starship is intended in most cases to come back to Earth. $\endgroup$ Commented Mar 7, 2021 at 2:50
  • $\begingroup$ So would the change in launch vehicle not impact Clipper's trajectory, timeline or mission design in any significant way? Would it use the same trajectory and get there at the same time? $\endgroup$
    – uhoh
    Commented Mar 7, 2021 at 2:58
  • $\begingroup$ Yes, it would, as described in the answer. $\endgroup$ Commented Mar 7, 2021 at 3:00
  • $\begingroup$ Okay, well it may take some time to see how this evolves, perhaps only speculation is possible at this point. The kick-focused uncertainty seems analogous to when Falcon Heavy was discussed, so I've added a supplementary answer based on that scenario. Thanks! $\endgroup$
    – uhoh
    Commented Mar 7, 2021 at 3:16

This is a supplementary answer, as it discusses Falcon Heavy and not Starship which I've asked about. I think it adds some background to the issue.

It depends a lot on the size and capability of the second stage that would be put on top of a Falcon Heavy.

A small kick state on top of FH would still require a gravitational assist from another planet, and this would add years to the mission and "physics" to the trajectory.

However if a large kick stage like a Centaur upper stage were launched by the Falcon Heavy, there seems to be enough delta-v to keep the mission on the same basic direct trajectory that would be used by the SLS interim Cryogenic Propulsion upper stage.

From Ars Technica's The billion-dollar question: How does the Clipper mission get to Europa? which was found in Congress may allow NASA to launch Europa Clipper on a Falcon Heavy:

A direct shot of a six-ton satellite to Jupiter requires a rocket with a lot of muscle. During the briefing, Culberson was told no commercial rocket can do this, even SpaceX’s Falcon Heavy rocket, which flew for the first time in February. (It is not clear whether NASA specifically asked SpaceX about the Falcon Heavy and Europa, as Goldstein said figures for all the commercial rockets were provided by a competitor to SpaceX, United Launch Alliance.) In the charts shown in the JPL conference room, engineers had modeled a Falcon Heavy with a small “kick stage,” but they had not considered alternatives, such as a Falcon Heavy with a more powerful Centaur upper stage for a direct-to-Jupiter mission.

Because the existing commercial rockets were not powerful enough, Goldstein said only NASA’s Space Launch System could get Clipper directly to Jupiter. The first version of this rocket, Block 1, can put 70 tons into low Earth orbit, and its Interim Cryogenic Propulsion upper stage has enough oomph to reach Jupiter in about three years. This is half the time of the commercial rockets, which will require more time to slingshot around inner Solar System planets to attain a Jupiter trajectory.


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