...you would need to know the initial bunkerage mass of reaction material (which becomes a reduction calculation over time, decreasingly affecting acceleration), and also cargo/crew mass, as that is usually (and quite correctly) a separate datum from the actual mass of the ship, as well as atmosphere, water, and food, and you need to as well consider the means of heating the ship—if you are relying on the drive engines to provide the requisite energy, it decreases the efficiency of those drives; if you rely on other means (battery-bank/radioisotope-reactor/something else), then you either need to incorporate that into your ship design, or account for its weight separately (yet another datum). As a note, heating is >absolutely necessary<, as vacuum is not only, well, a void (negligible air and water; will remove same from a habitat unless perfectly sealed; perfect seals are impossible, so attention is instead paid to making the seals as good as possible so as to minimize lossage), it is also only a few degrees above absolute zero, and any object located in a void >rapidly< cools to nearly the same temperature—not a survivable condition. Even crew carried as cargo in some form of suspended animation, unless it involves some sort of time manipulation (in which case, the transit times are moot), still need to be kept at a >much< higher temperature, and at a fairly high environmental pressure, else the frozen tissues suffer degradation from other than the current limiting (and deal-breaking) issue of cell-rupturing ice crystals.

I can try asking among my friends, one of whom maintains the local university's physics department's computers and network. If I get any information, though, it won't be for a few days at best. Do you have time for me to ask? I've only worked with intra-system inter-planetary transits, and I >really< don't remember the math for that, even, so I'm not much help in myself to the question of inter-stellar mechanics.

That said, it seems to me that you might also need to know the vectors of both systems, both relative to a "fixed" referent, such as the galaxy, and relative to each other. At that distance, and given the large interval on which the journey would be made (again, referent to the rest of the galaxy; okay, not so big on that scale, either, but still) the possibility of missing the target due to considering it static when, in fast, it's moving fairly rapidly and potentially in very different directions would be, if you would pardon the phrase, cosmically embarrassing.

-Liz

Successor to the LToC

I knew I was forgetting something important related to this! Yes, the principle criticism to the concept of high-C-fractional travel. Thank you!

re: the concept of rotating crew (per Scott's comment, especially): You would have about a third of your crew on actual duty at any given time >anyway< without "hibernation", just due to standard shift rotation. *being just >slightly< oblivious to what you actually intended* ~__^ Seriously, though, if you had suspended animation technology available, you likely wouldn't >need< to have a full third of your crew awake at any given time, as the majority of the crew, again, given that technology, can be composed of specialists not cross-trained in starship operation. even given the assumption that you >really< want to spend the tens of millions of dollars required to train them in the extra skill-set, there just isn't the need, as you only need a couple of people each waking duty rotation to maintain and run the ship, unless something goes wrong, in which case, you either have enough time to awaken additional help, or you are likely dead anyway and the point is somewhat moot. Additionally, it's better from a small-group psychological and sociological standpoint to have relatively few people on duty at one time, and the rest in SA and thus reducing the overall group levels of stress due to being together in a constrained space for an extended time. This particular consideration is actually one of the big ones in planning for mars missions, and is one of the big obstacles. The solution has been to select for mission crew those who show an extremely rare ability to handle just such conditions. Finding such individuals is difficult, as the quality is hard to effectively test for. It might be supposed, though, that the selection for flight operations crew for such a long, dangerous mission would very much focus on such individuals, and, in the interest of cost-effectiveness, >only< train for primary flight operations those few who need to occupy that role, and leave the rest of the crew positions to specialists who lack that quality, but who have obtained credentials and capabilities in other, less-demanding (in this sense, at least) areas.

tl;dr: You don't need to spend the money and the effort to make your whole crew capable of running flight operations, and therefore do not need to have even a full third awake at any given time. Until you reach your destination, they are best handled as very fragile cargo, leaving the professional space jockeys to handle the actual journey unhindered.

re: inertial compensators and Heisenberg compensators, and such: No! No blocks of solid platinum! No, no no! >.< Silly-"Science!" workarounds are best left out of a story unless you >NEED< to have them. They detract from the story, no matter the situation, and are only justifiable if there is no way to >avoid< inclusion and still have the story make sense. Even then, they are black boxes that are best treated as little as possible. One of the problems that Trek-science has developed in its march away from real-world physics is the fact that writers for the episodes lost sight of that fact, requiring ever-greater convolutions to incorporate the various bits into new stories, and in turn causing such a growth in complexity that the whole mess has massive >technological< inconsistencies within itself. When a new story is rendered unbelievable due to the author forgetting some detain that was really only mentioned in one story a couple of decades ago, but that is the foundation for several other technologies that were "invented" based on or even just taking advantage of it, and the new author, assuming these contravenes the former, it makes the whole situation seem more artificial and less believable than it should.

tl;dr: "Extra-tech" should be kept to a minimum, as it raises the threshold for suspension of disbelief, making the story harder to "get into".

In that vein, Khadijah, remember that most science fiction authors tend to >massively< gloss over the numbers for celestial mechanics and travel between points A and B. The reason for this is that, as has been shown, those numbers are >complicated<, and most science fiction authors, even those who have appropriate physics or mathematics degrees, don't want to write a goodly-sized novelette just to justify their numbers before getting to the actual story. Those that >do< dwell on the numbers tend, no matter whether they are considered a good author otherwise, to be called on that exact point. Witness David Weber: he's reasonably well-thought of by space opera and military SF writers and fans (with exceptions; taste is a factor in that, as are issues with other aspects of his work), but he is >routinely criticized for the really dumb errors in his math and for some technical aspects of his extrapolated physics and technology that he >over-includes<, and thus sets himself up for critique of by people who actually work in related fields, whether they themselves are right or wrong. In short, it's better if you just figure something that sounds reasonable, provides just enough of the framework that you need to hang your story from, check about that specific something if you feel particularly uncertain or if the detail would make for more than just a mcguffin, and then just write the part of the story that's actually interesting to you.

-Liz

Successor to the LToC