Ion Drives

Previously, I talked about ions. Remember, they are atoms that have either more or less electrons than protons. For ion drives, positive ions, also called cations, are used to propel the craft ahead.

The ions are created in a chamber where the electrons are stripped from an atom or molecule (many times xenon or ammonia, depending on the thruster type), then are accelerated via an electrostatic or an electromagnetic field.

Ion drives have a very high specific impulse, which means they are very efficient engines. Specific impulse is the ratio between the spacecraft's thrust (the force at which the spacecraft is being pushed along) and the weight of the fuel used to create that thrust).

However, the thrust from an ion engine is small since ions themselves are rather tiny. Ion engines are not great from getting place to place quickly in the solar system. Typically, ion drives will be used for space stations for maneuvering or for deep space probes. Though the thrust is tiny, over time, that thrust can add up to a large velocity for the spacecraft.

Deep Space 1

Via NASA

Schematic of Deep Space 1

via NASA

Star Wars and Physics

First of all, let me point out that I love Star Wars. I am old enough that the first three movies came out after I was born, so I grew up with the legacy of Luke, Leia, Han, Chewbacca, and all the rest. Everyone has already talked about how Han Solo's line about making the Kessel Run in less than 12 parsecs is inaccurate since a parsec is a distance and if the Kessel Run is less than 12 parsecs in distance, then big deal. But that is not what I want to talk about. I'm not going to talk about lightsabers or the force, since they are part of the mythos.

I want to talk about when ships are docking on the Death Star.

In almost every scene I've seen of the Millennium Falcon or the Imperial Shuttle landing in one of the cargo bays on the Death Star, I notice two things.

One, they never show a force field being deactivated, which is not that big a deal since a force field technically is invisible.

Two, when the Millenium Falcon or the Imperial Shuttle is coming in and landing, there are people in the cargo bay. This is important because if the force field is down, the cargo bay will have no atmosphere in it. Granted, the stormtroopers or whomever could have some sort of scuba gear or self-contained breathing in their armor, but when the Millennium Falcon leaves in Episode IV, Luke, Leia, Han, and Chewbacca run to the ship without any difficulty breathing. But they leave without deactivating a force field. So did the Millennium Falcon just fly through a force field? Is there something across the opening of the cargo bay that prevents the atmosphere from leaving but allows a ship to go through? That seems a little far-fetched, but again, it is science fiction.

So is there a force field across the opening of the cargo bay to hold in the atmosphere? If there isn't, how are the stormtroopers able to breathe and for that matter, our heroes when they are leaving? If there is, how is the Millennium Falcon or the Imperial Shuttle able to travel through the force field without a problem?

Warp Drive

I'm going to detour a little bit from talking about the Sun to talk about something new that has come up this week: NASA Physicist unveils warp-drive craft design

Now, if you read the article, make sure you note that this is what it would look like, much like what the NX-01 Enterprise looked like from Star Trek: Enterprise TV Series.

We are not capable of creating an engine that can allow so-called faster-than-light travel.

 

I call this so-called because technically, warp drive does not allow faster-than-light travel, but apparent faster-than-light travel.  What warp drive does is warps the space ahead and back of the ship, compressing space in front and expanding space in back.  This would allow the ship apparently to move faster than light.

Special relativity tells us that faster-than-light travel is impossible in normal space, but warp drive gets around this by creating a bubble around the ship, again warping space around the bubble.

Faster-than-light travel is impossible in normal space because relativity states that the closer to the speed of light an object gets, the heavier it gets.  At the speed of light, any object with mass has an infinite mass. Therefore, to accelerate something to the speed of light requires infinite energy.

Conceptually, this is what warp drive would look like.

As you can see in front of the Enterprise, space is compressed and behind the Enterprise, it is expanded.  Unfortunately, the physics to allow warping of space is unknown and probably won't be known for a few decades or centuries.