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

If you're going to set your story someplace we already know something about -- like [[Useful Notes/Mars|Mars]] or [[Useful Notes/Local Stars|Alpha Centauri]] -- for goodness' sake, read up on what we know about the place before you start writing! We've sent space probes to [[Pluto Is Expendable|every planet]] in the solar system, we've accrued reams of data on just about every star that has a name, we've even mapped out the interstellar medium in our neck of the galaxy. The data are out there, and thanks to the Internet they're not even hard to acquire any more.

 

 

In other words: Don't give 'em the opportunity to make a [[Did Not Do the Research]] entry for your story's TV Tropes page.

=== Special [[Useful Notes/Relativity|Relativity]] ===

 

 

And there's where we run into problems. Because above about a tenth of the speed of light, acceleration doesn't affect velocity in a straightforward manner any more. Your clock runs [[Time Dilation|a little slower]] to a fixed observer than it does to you. Your momentum is slightly higher to a fixed observer than your acceleration history says it should be. The universe shrinks slightly in the direction you're moving. In short, you run smack-dab into ''special [[Useful Notes/Relativity|Relativity]]'', and now the math gets a '''lot''' more complicated. For one, the change in your velocity per second, given a constant acceleration from your space ship's reference frame, now depends on your current velocity -- which turns the relationship between the two into a first-order differential equation.

* The [[Orion Drive]]

* Controlled nuclear fusion engines

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 don't have that much better an exhaust velocity than chemical engines, and require shielding to protect the crew (and the ship's more delicate electronics) from their radioactivity. 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's nuclear putt-putt motor 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.

 

== Deviation: Limiting the Damage ==

 

 

But hold on. You've also opened up a can of worms.