* FridgeLogic: The Messiah has an Orion Propulsion System and was assembled in space. It's way too small to be one. (Orion was a military project to build a deep space craft in the late 50's, it works by exploding nuclear bombs behind a very thick metal plate and getting hit by the explosion. Most designs are assembled on the Earth and are about 1 mile in Radius).
** Further, if it was an Orion Craft, which could achieve the course required by the ship to not only reach the comet, but match course with it, there would be a heck of a lot more nuclear weapons on the ship. No reason to not simply try again at altering the course of the comet fragments.
*** Other than running out of personnel, you mean?
*** If she's the size you need to be an actual ''Orion'' vehicle, then that's not an issue. Put a larger crew and the consumables needed to sustain them aboard the ship. Also, [[TooDumbToLive teach them to keep their sun visors down when it might be a good idea to do so.]]
* The ''Messiah'' was a ''big'' ship, as it needed to carry everything the astronauts would need for what's essentially a deep-space journey of roughly one year. To that end (under the heading of CrazyPrepared) why not load several cruise missiles adapted for spaceflight and destroy the comet by using visual guidance to shatter it far out in space by hitting it with a couple to create fissures '''and then''' flying a nuke inside? Better yet, why not just tell the world, use Earth's combined resources to build a fleet of ''Messiah''-'''class''' ships to hit the comet as mentioned above, or (just as good) have the fleet soft-land one of the vessels, lock it on the surface, and use the ship's Orion Drive to divert it by fractionally adjusting its course away from Earth?
** Of course, you want to make sure that the astronauts give themselves enough distance from the comet '''before''' they detonate the nukes.
** If you're going to soft-land engines on the comet to make it steerable, then Orions probably aren't the best choice; running them would be like repeatedly hitting the comet with a very large hammer. A better choice would be a steam rocket: you don't need to lift any reaction mass because you'd just use the local landscape.
* Also, why doesn't the ''Messiah'' have '''at least''' one ''Soyuz'' capsule as an escape vehicle? Not only would they have been useful (only one person would have been required to make a HeroicSacrifice), but they could have jury-rigged the radio equipment inside those capsules to re-establish contact with Earth.
* The design of ''Messiah'' was logical to the time period. They appeared to literally scavenge new and old components, including a Shuttle Orbiter crew compartment as the main cockpit, to kludge together something to fly within a year.
** The problem ob building the ''Messiah'' could have been solved easily if - instead of hiding the news of the comet for a year and the U.S. and Russia building the craft in secret - they had informed the entire world, and used the resources of the planet to build a fleet of ''Messiah''-class ships to go out and intercept the comet, do a time-on-target barrage with the missiles and then nuke the comet from within by flying nukes in through the fissures (as suggested above)? Not only do you get a far better chance of stopping the comet in deep space, but if there's any injuries or damaged ships, others could take on their crews and tow the damaged ship back in... and even better, Earth now realized that ''they have a fleet of spaceships that they can operate in space for months at a time'', and the worldwide era of space travel begins!
* Why did all of the people on the highway ''stay in the area'', only to be killed there when the tsunami hit? Why didn't they all just evacuate weeks before just out of an overabundance of caution, and even if they lost their homes, they would still be alive and capable of starting new lives?
* FridgeHorror: If no one over the age of fifty would be selected, then the sheer number of older U.S. citizens who were either euthanized (to spare them from suffering through the horrors of the comet strikes) or given the means to commit suicide would have made the Holocaust look like a small-town Santa Claus parade.