Almost twelve years ago NASA launched the Deep Space 1 Probe. The first interplanetary device to demonstrate successful ion propulsion in space. Ion engines were by no means new. In fact, they are the given explanation for how the Star Trek shuttlecraft are powered in the original series. The idea is to use electric power to accelerate ions, something only possible in an engine in the vacuum of space. What results is a much higher specific impulse, a measure used to define the efficiency of chemical propelled rockets. The more impulse per mass of propellant used, the more efficient the propulsion.
The ion propulsion system is what specifically gave DS1 its efficiency, allowing it to travel at the same speed for about half the mass of conventional space propulsion. However, its launch was not without problems. On board it carried a multitude of different payload devices, most of which had never been tested in space. The engine also failed soon after it first started though they were able to restart it successfully and the engine continued thrust for almost two years.
As someone who has dealt with aircraft payload devices as well as engine hiccups its hard to imagine what this is like. Of course you do as much software simulation and ground testing as possible, but if the conditions at high altitude are different enough from those at ground, I'm sure there's magnitudes of difference between ground and lab testing versus space. Then how do you troubleshoot? There are some serious advantages to being able to take pieces of your hardware and inspect them or replace them. The advantages of being able to look everything over visually, then pull things apart. Your satellite likely doesn't even have an arm or anything you could use on itself. At least a deep sea robot device you could potentially get it to surface in order to work on it, but your satellite or space probe is never coming back.
Seems like the pure basics of exploration. Before humans went out in ships or on trade missions early tribes moved and explored mostly when they needed to migrate. When food or resources were scarce they journied on, not knowing what lay ahead only to find new places to survive, how they theorize Easter Island was originally settled. Technology gives us the advantage of not risking human life in many of these endeavors, but the payoff is still enormous.
Since DS1 numerous other devices have employed ion propulsion in space. It will be interesting to see how far this technology will take us; physically, and to what limits of our dreams.