Some ideas for a Mercury rover

In the last few years, I’ve written a few posts on ideas for various space missions: Some ideas for small lunar landers, A fun idea for a moon mission, and Some ideas for space missions.  Here’s one more.

I forget exactly why, but I started thinking about landing a rover on Mercury.  There are several challenges to that, mainly having months of 430℃ temperatures followed by months of -180℃ temperatures.  So this was my first idea that would be awesome but not practical. 

This mission would have four components.  The main one would be the rover, which would be powered by RTGs which would power the rover as well as keep it warm as it traveled around the night side of Mercury.  To take photographs, it would be equipped with spotlights.  The way the rover would land on Mercury would be with a sky crane-ish rocket thing, but instead of dropping the rover then flying off to crash, it would fly back up to a mothercraft that would orbit Mercury doing other science as well as being a communication link between Earth and the rover.  As dawn approached where the rover was, this crane-rocket-thing would fly back down, pick up the rover, and fly it a few hundred kilometers to the west, then return to the mothercraft to refuel.  Also, at the mothercraft it would pick up an empty sample case, and during the transfer, a little robotic arm would attach it to the rover and pick up a filled sample case.  All these sample cases would be transferred to the fourth component, a sample return capsule that would return many kilograms of samples to Earth.

While that is a fun idea, there are some issues with it.  Mainly if the crane-rocket-thing crashes, or can’t pick up the rover, the mission is over.  And while our probes are getting smarter, there are probably too many variables and too many things that could go wrong for that to be reliably automated.  So I wondered if there was a way with current technology to land a rover on Mercury. 

One possibility would be to land a rover with a garage that could shield it from the heat of the day.  The problem with that is that the rover would be limited in the area it could explore.  Unless the garage is on some sort of trailer the rover could move every few months.  But unless there are a lot of perfectly flat areas to set up the garage, it’s going to be tough to have good seals.  Like, I imagine there’d be an expanding element on the bottom of the walls to go over rocks and uneven areas.  That would probably be painful but doable once, but doing so multiple times would just increase the chance of a gap letting light in. 

My current idea, is just a squat lander with some instruments with the rover on top of it.  This would land on the night side to give it time to unfold a giant sunshade.  I picture a pole in the middle of the rover, with a turn and tilt mechanism at the top.  The sunshade would unfold, and then be lowered down to shield the lander and rover from the dawn.  As the sun rose in the sky, it would be moved to keep everything covered.  So for the first few months, the rover would still be on the lander.  This would give time to get everything in working order and to do some science, like seeing how fast the surface heats up.  Once the sun set, and the ground cooled, the rover would drive off the lander and head a few kilometers away.  Maybe even hiding behind a hill.  Because it would be interesting to see what happens to the lander when exposed to the full might of the Mercurian sun.  I imagine thermometers in various parts of the lander that would report how fast they heat up.  But to be able to report them, there would have to be batteries to power the radio, and depending on how they fail in the heat, they might explode, which is why you’d want the rover a few kilometers away. 

While the rover could travel around during the night doing science, it would park at an interesting site for the day.  Maybe it would have a drill to take samples from a couple of meters down, so it would be in one spot for a couple months to allow it to drill that deep.  But if you make the sunshade big enough, you could still travel during the day.  It would just be very slowly.  Like, if the shade extended a couple of meters in front of the rover, you could wait for the ground to cool and then creep forward ten centimeters or so.  And then wait however many hours for the now shaded ground to cool enough to creep forward again.  It may only move a meter or so a week, but it wouldn’t be still waiting for sundown.

Of course, given the slow rotation of Mercury, it would mean that there would be long periods of time the rover wouldn’t be in sight of Earth.  Which means there would need to be an orbiter to act as a relay.  But then if the orbiter dies for whatever reason, the mission is over.  So there may need to be several orbiters around Mercury that can all act as relays while doing their own missions. 

There is a great deal we don’t know about Mercury, and a rover would fill in some blanks.  But given that it would need RTGs, a powerful rocket to get it in to Mercury, as well as some orbiters, it would be rather expensive to fill those blanks.  Still, as humans spread out into the solar system, it’s only a matter of time before we start landing things on Mercury.  Maybe whatever does end up there will look something like this.  I hope I live long enough to see.