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Enceladus Mission Options
JRehling
post Mar 16 2018, 02:54 PM
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I started a new topic here as Enceladus is among those worlds in the top handful likely to attract a dedicated mission in the coming decades, but it has gotten little attention – on UMSF, anyways – as a destination, although the science of Enceladus has gotten plenty of attention. Meanwhile, the possible mission concepts for Enceladus are unique and uniquely broad; any mission exploring Enceladus is likely to employ an utterly different architecture from any mission to any other world with the possible (but unlikely) exception of Europa.

By far the concept closest to realization now is the Enceladus Life Signatures and Habitability (ELSAH) New Frontiers proposal led by Chris McKay at NASA Ames. This essentially finished third or fourth in the last New Frontiers selection process and received funding for further development. If New Frontiers launches continue at the pace of one every five years, one could naively project that ELSAH (note the similarity to the name of a popular Disney princess) might launch in 2031 or 2036. That's probably somewhere between optimistic and unfounded, but it seems reasonable that Enceladus could garner a mission or a share of a Saturn system mission concept before 2050.

A few Enceladus-bound missions have gotten some level of attention, sporting a collection of "E"-led acronyms and a spectrum of mission concepts ranging from an Enceladus lander to Saturn orbiters that provide frequent Enceladus rendezvous (in some cases with duties split between Enceladus and Titan) to sample return missions that will snatch geyser/plume ejecta and return it to Earth. Some of these missions have entered Discovery competition without success, but there's no guarantee that this reflects a weakness in the concept as opposed to the maturity of the proposal or other factors.

The musing that led me to start this thread came from a newfound appreciation of the E ring. While missions to sample the plumes depend upon their continuous activity – a prospect that has been supported by Cassini but can't be guaranteed for any future mission – the E ring is certainly enduring and extensive, and a mission that samples the E ring as well as the active plumes, which are colocated within the E ring, is sure to find particles that originated from plumes in the recent past.

Sadly, there's an inevitably long flight time for any possible Enceladus mission, and a very long duration for any sample return, so the endgame for Enceladus exploration is likely to run deep into this century and makes any of us mortal spectators likely here for just the beginning of the exploration of what could turn out to be the most fascinating object in the solar system. If only, like Mars, Enceladus permitted flight times of a few months, Enceladus might even dominate exploration budgets in the near future.
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Explorer1
post Mar 16 2018, 03:05 PM
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QUOTE (JRehling @ Mar 16 2018, 09:54 AM) *
Sadly, there's an inevitably long flight time for any possible Enceladus mission, and a very long duration for any sample return, so the endgame for Enceladus exploration is likely to run deep into this century and makes any of us mortal spectators likely here for just the beginning of the exploration of what could turn out to be the most fascinating object in the solar system. If only, like Mars, Enceladus permitted flight times of a few months, Enceladus might even dominate exploration budgets in the near future.


Would any of the launchers currently on the drawing board improve transit times significantly? I know it's speculation, but where will (for example) BFR be by 2036, given the current pace? I'm still young so perhaps I'm just being too optimistic/impatient....
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JRehling
post Mar 17 2018, 06:01 PM
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Larger launchers certainly provide shorter travel times if you use them that way, but it's not straightforward. Nobody's interested in a single high-speed Enceladus flyby, so a faster outward trip requires more delta-v to brake, which means more engine+fuel mass, which hurts your margins for payload. For any flight plan, more speed means less payload mass, so a bigger launcher might be converted to larger, more capable spacecraft instead of shorter travel times.

It seems likely that most mission plans will involve inner-solar system gravity assists and some more billiards in Saturn orbit, probably involving Titan.

Maybe someday we'll see aerobraking in an outer solar system mission: Titan would be a great resource for that, I think, with a large scale height and not such a problematic gravity well as Saturn or Uranus/Neptune. Still, you need to haul something to enable that aerobraking to optimum benefit.
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vjkane
post Mar 18 2018, 08:53 PM
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"By far the concept closest to realization now is the Enceladus Life Signatures and Habitability (ELSAH) New Frontiers proposal led by Chris McKay at NASA Ames. This essentially finished third or fourth in the last New Frontiers selection process and received funding for further development."

I wouldn't draw the conclusion that ELSAH finished third or fourth. While NASA funded further development of a specific technological aspect, that doesn't mean that the mission was judged to be Category 1 (highest category indicated that it is fully selectable). Information from VEXAG indicates that among the three proposed Venus missions, only the VOX orbiter was judged to be Category 1. Yet it was Lori Glaze's VICI lander proposal that led to funding for further technical development of a single issue with the proposed landers' instruments.

Anyone interested in the issues for Enceladus missions should read Jonathan Lunine's summary of their ELF proposal debrief on the issues raised that presumably led it not to be selected.

Lunine ELF OPAG presentation


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