A “nearly wise” science-fiction fan has compiled this list of common misconceptions about space travel — some obvious, some not, some grammatical, some not:
- Space is not an ocean. In particular, space is not two-dimensional, there is no friction in space, and spacecraft will not have their decks laid out as if they were seagoing vessels.
- Space is three dimensional. Spacecraft are not limited to moving on a surface like a boat, they can go “up” and “down.” They are not even limited like a aircraft, the latter is limited to how far up and down they can go. A spacecraft can theoretically fly to infinity in any given direction.
There is no limit on their orientation either. If you saw the Starship Enterprise approaching the Starship Intrepid and one was “upside down” with respect to another, you might think this was wrong but in reality there is nothing preventing this. Even worse: the nose of the other spacecraft might not even be pointed in the direction the ship is flying.
- Rockets are not boats. With a scientifically accurate rocket, the direction of “down” will be in the same direction that the rocket exhaust is shooting. In other words, a spacecraft will have the general internal arrangement of a skyscraper, not that of a passenger airplane.
- Rockets are not fighter planes. It is impossible to make swooping maneuvers without an atmosphere and wings.
- Rockets are not arrows. Spacecraft do not necessarily travel in the direction their nose is pointing.
- Rockets got wings. If your rocket has a multi-megawatt power plant, an absurdly high thrust thermal rocket propulsion system, or directed energy weapons it will need huge heat radiators to purge all the waste heat. Otherwise the rocket will melt or even vaporize. Radiators look like large wings or arrays of panels. The necessity of radiators a real problem for warships since radiators are pathetically vulnerable to hostile weapons fire.
- Rockets don’t got windows. Spacecraft have no need of windows or portholes, for much the same reason as a submarine.
- There is no friction in space. In space, if a ship turns off its engines it will maintain its current velocity for the rest of eternity (unless is crashes into a planet or something).
Acceleration and deceleration are symmetrical. This means if your spacecraft spends an hour accelerating to a speed of 1000 meters per second, it is going to take roughly another hour to decelerate to a stop. You cannot “put on the brakes” and suddenly stop, like you can do with a boat or an automobile. (I say “roughly” because as you accelerate your ship looses mass due to expending reaction mass, so it becomes easier to decelerate. But this is a complicating detail you can ignore for now)
- Fuel is not propellent. Mass is violently thrown away in the form of the rocket’s exhaust and the reaction accelerates the rocket forward. This mass is of course the “reaction mass.” It is sometimes also called “remass” or “propellant.”
The “fuel” is what is burned or whatever to generated the energy to expel the reaction mass. For example, in a classic atomic rocket, the fuel is the uranium-235 rods in the nuclear reactor, the reaction mass is the hydrogen gas heated in the reactor and expelled from the exhaust nozzle.
There are only a few confusing cases where the fuel and the reaction mass are the same thing. This is the case with chemical rockets such as the Space Shuttle and the Saturn 5, which is how the misconception started in the first place.
- There ain’t no stealth in space. In space, there is no practical way to hide your military spacecraft from detection by the enemy.
- There is no sound in space. There is no air in space so neither is there sound.
- Mass is not weight. The Space Shuttle may be floating next to the station with a weight of zero, but it still has a mass of 90 metric tons. If it is stationary and you pushed on it, there will be very little effect.
- Free fall is not zero gravity. Technically, people in, say, the Space Station are not in “zero gravity.” The gravity at the altitude of the Station is about as strong as it is on Terra’s surface (it is about 93% of full gravity). The reason that everybody floats around is because they are in a state of “free fall.” If you were in an elevator, and the cable snapped, you too would be in a state of free fall and would float around. At least until you hit.
- No vacuum pops. And if you were suddenly thrown into the vacuum of space without a spacesuit, you would not pop like a balloon.
- They don’t want our water. Aliens invading Terra to steal our water makes about as much sense as Eskimos invading Central America to steal their ice. Water is one of the most common substances “out there.”