What is this car hatch?

I was surprised to see what looked like a gas tank hatch in front of the driver’s door on this car (an Audi, IIRC). On the passenger side rear there is a gas hatch where I’d expect to see it.

Any ideas what it is? A few friends were stumped.

It’s probably a plug in hybrid, so that’s where the socket is to plug in to recharge the battery.

Plug in port for a hybrid? That’s where it is on my wife’s Ford C-Max.

Audi makes some plug in hybrids, both a gas tank and an electric plug.

Cool! Electric cars are pretty rare around here IME.

I believe that is a Volvo XC90 hybrid.

Outer torpedo door?

Hidey-hole?

Many vehicles have sophisticated computer systems now. That’s where you load the hamsters.

Hybrid plug

A secondary storage place for your trunk monkey?

Heh. I’m not a car guy. When I took the picture I looked at the rear of the car, and I remember thinking, “oh, one of those safe cars” which to me would be an Audi or Volvo.

It’s an RCS thruster — for Reaction Control System, aka a side thruster, or yaw thruster. Very helpful, e.g. for parallel parking.

Image >> https://upload.wikimedia.org/wikipedia/commons/f/f7/Shuttle_front_RCS.jpg