Star Trek, however much we love it, was sometimes guilty with a certain exaggeration and more than its share of inconsistency. In some episodes, ion drives were advanced technology and in others they were outdated. Decide!
ESA JAXA's BepiColombo probe is on its way to Mercury with four ion engines developed by a company called QinetiQ. But unlike the ion drive of the notorious episode "Spock's Brain," BepiColombo will take more than seven years to get to Mercury. That's because these ion drives are real.
The ship actually consists of two spaceships in one with two different Mercury missions. The Mercury Planet orbiter will study the surface while the magnetospheric orbiter will study the magnetic field of the small planet. Watch a video of the mission below. The second video shows [Neil Wallace] how ion propulsion ̵
According to [Wallace]the higher efficiency of the ion motors makes the mission possible. A 6.5-meter-high vehicle that weighs about 9,000 pounds at take-off would be unbearable without ion propulsion. The ship will also use gravitational aids from Earth, Venus and Mercury.
The ion engines are only about nine inches tall and use xenon gas. Solar energy delivers 4.5 kW to ionize and accelerate xenon to over 100,000 miles per hour. Of course, xenon atoms do not weigh much, so the thrust is only 145 mN. ANSI A117.1 (Standard for Accessible Buildings and Facilities) requires that interior doors do not require more than 22.22 m (22.22 mN) of opening or closing. That's only five pounds of power, so the engines do not produce enough to open your bedroom door. In space, however, these tiny forces add up, and over time they will act on the massive spacecraft and brake uninterruptedly against the Sun's pull until the ship orbits Mercury.
Chemical missiles obviously have a much greater boost, but use 10 to 20 times the fuel to do the same job. It is also difficult to keep a high-energy chemical rocket running for thousands of hours without failing. In addition, this fuel contributes to the weight of the vehicle. Ironically, NASA's SERT ion engines, which were tested in the 1960s and 1970s, used mercury as a fuel. Xenon, however, is less prone to wear off the accelerator grids.
Sometimes less is more in space flight. For example, an electron provides an easier way to get smaller satellites into orbit. If you want a more conventional rocket propulsion, do it the way we did when we were kids and use water.