EDIT: David Birchler mentioned in the comments that an implant is not required. The technology is called galvanic vestibular stimulation and it can stimulate the sensation of pitch, roll, and yaw. Since surgery is not required, it sounds like this really IS doable as a countermeasure for dizziness on landing (perhaps combined with training) and the sensation of coriolis in a short arm centrifuge. In fact, for the former, it looks like this is already being tested as a training tool for astronauts: http://nsbri.org/researches/galvanic-vestibular-stimulation-augmented-training-for-exploration-class-missions/
and here, it shows that GVS training can allow quicker adaption to different vestibular environments: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4458607/
Here’s a company which is developing the tech (along with Mayo Clinic) synced to Virtual Reality: VMocion
For a few years, now, I’ve been convinced that one of the best ways of making human spaceflight affordable and even competitive with robotic spaceflight in some areas is by engineering as close to the human as possible.
For instance, to solve radiation issues, you could shield the entire spacecraft. But this requires a lot of mass. Mass-wise, better is to shield just the habitable areas. Better still is to focus on areas the crew spends the most time in, like the sleeping quarters. Better still (though weird and awkward) might be a garment with radiation shielding. And yet we can do better still: radiation countermeasures in drug form, which protects at the cellular level. Drugs like Amifostine. (But we need better ones.) Or even closer, the nuclear (as in, cell nucleus) level: You could propose either genetically modifying people themselves to produce radioprotectants (or perhaps engineering our microbiome to produce radioprotectants without requiring engineering of actual humans). In each case, the closer to the human you engineer, the lower the mass and ultimately the cheaper it is (at scale).
Another example of this would be microgravity. There have been drugs that have been used to help maintain bone density, such as those used for osteoporosis, particularly Bisphosphonates, which have already been tried on ISS (although there are more powerful drugs available which haven’t been tried, such as Forteo). But exercise seems largely sufficient for the usual durations. And on a larger scale, you could try internal short-arm centrifuges. And on a larger scale, tethers for artificial gravity. But at each point, the mass overhead becomes greater. So I prefer the drug-based countermeasures if possible.
Another effect is a sense of dizziness after astronauts return from long stints in microgravity. The dizziness doesn’t last too long, but it’s feared to prevent rapid escape from the vehicle after landing (say, on Mars) if there’s a problem. I think this is a corner-case-of-a-corner-case, i.e. you have to have a survivable landing but still have to have a reason to immediately exit the vehicle AND be close enough to other help while also not being too injured too move AND you have to be so dizzy that you can’t exit the vehicle.
But let’s say that’s the only showstopper to microgravity. (and it’s not a showstopper, but let’s say it is) Another possibility is vestibular implants. Some people actually have damage to their vestibular system from disease or injury, and so they can be given an artificial vestibular implant, using external MEMS gyros attached to their head, to restore a sense of balance:
But because the signal is now synthesized, you can now modify it. You can impose the feeling of gravity on an astronaut in microgravity, prepping the astronaut for landing. Or perhaps smoothing out the strong Coriolis effect from short-arm centrifuges. You should be able to reduce the dizziness an astronaut feels after returning to gravity.
Also, it’d allow for some crazily-immersive VR.
Now, I personally think that the brain is already sophisticated enough that we can actually train ourselves to tolerate the Coriolis forces (and this is borne out of a study from MIT), and probably also learn how to combat the dizziness that is felt upon landing (perhaps by regularly spinning around just in the air while in microgravity). So I don’t think this is purely necessary. But I do think that long-term, we need to start thinking in this direction in order to make mass human spaceflight more feasible. Human spaceflight seems intrinsically expensive because of all the overhead required for humans in space versus robots. But we can engineer ourselves, much like we developed clothing to enable living in colder climates.