So You Want To/Write a Hard Science Fiction Story With Space Travel: Difference between revisions

 

With such a stultifying mass ratio ''just'' to get into Earth orbit, you can see why flying to other planets in a matter of days -- or worse, flying to another star within a human lifetime -- just isn't practical for modern chemically-propelled rockets. Most hard SF authors will solve this problem by using more exotic forms of rocket propulsion which have much much higher exhaust velocities, or which can derive their propellant from someplace other than the rocket's fuel tanks. These include:

* Nuclear fission (NERVA) engines

* Ion engines, such as those on the ''Dawn'' and ''Deep Space One'' spacecraft

* Controlled nuclear fusion engines

* [[Ramscoop|Ramscoops]]

With the exception of ion engines, all of these are mere drawing-board designs at present, and all of them have practical problems. NERVA engines require shielding to protect the crew (and the ship's more delicate electronics) from their radioactivity, but saving weight is so important that there is only enough shielding to protect a cone in front of the reactor. Ion engines have extremely low thrust levels (the engines on the ''Dawn'' spacecraft can, at max throttle, produce about 1/3 of an ounce of thrust). Orion drive requires an enormous pusher plate that dramatically increases the dead weight the spacecraft has to carry. Controlled nuclear fusion has never been accomplished, at least not in a way that produces more energy than it consumes. Ramscoops rely not only on the controlled nuclear fusion of light hydrogen (which is even trickier than the controlled nuclear fusion of heavy hydrogen), but also on the ability to collect the extremely rarefied interstellar gas without inducing significant drag, which might not even be possible.