Sci-fi Weapons, Vehicles and Equipment

The infact do.

Anyways, if we have already established that we're cheating at the laws of physics just to get to the planet, nevermind getting on the planet, I don't see why we're suddenly Lawful Stupid and bidden to obey the laws once we're on xeno firma.

Because the ways to cheat physics for FTL travel are documented to in fact exist.

As far as we can tell, anti-gravity does not.

In addition to that FTL is pretty much required to tell a good sci-fi story, having a capital ship lifting off from planet-side is very much not so.

edited 28th Apr '16 8:58:32 PM by Imca

It is necessary if I want my story to have massive starships which can land on and take off from planets.

At which point we can opt to use the softer side of sci-fi to get around the real world limitations.

Immy: Lets go soft side sci-fi to say Titan Fall. They show the ships being able to use their tech to go from space to floating above the planet. There is no reason to exclude it from Sci-fi stories unless your geared towards realism. If we were trying to do Titan Fall with realism it would look a bit different and would be less Titan Fall and more real robot.

It always bothers me how, in most sci-fi, capital ships can just loiter in the air, perfectly stationary, for an indefinite period of time. If I were building a 'verse, I'd have it be so that only craft of a certain weight class or below that were specially designed to operate in-atmosphere could do that. Sort of like a space-equivalent of littoral craft. More believable and interesting that way.

Gault: Also a good option if that is what your after.

I have to say, the fighters in the New Independence Day movie are badass as hell. Hell all of the tech humanity reversed engineered is Rule of Cool taken Up To Eleven.

Still not sure if even a united Humanity could have that tech be so widespread in only Twenty years, but I'm not complaining.

Capital ships in gravity wells makes a kind of sense actually. After all, if you can induce artificial gravity for the benefit of your crew, you probably have the know-how to overcome natural gravity.

I don't think so. Ships in my 'verse have artificial gravity, but it works consistently with the laws of physics in the sense that a ship cannot negate it's own weight using onboard artificial gravity generators because of being a closed system. Essentially, you can't expect a ship to use AG to pull on itself. All the forces already have to balance out. It works for people and objects onboard the ship, but the AG generators are affixed to it's actual superstructure so you would need AG generators on the planet to keep the capital ship floating in the air.

edited 29th Apr '16 1:52:47 AM by Gault

Each to their own of course.

Tactical: I am actually looking forward to the film.

Not necessarily. The Saturn V rocket with Apollo capsule only needed to be built for thrust whereas the capsule itself had to withstand both the stresses of re-entry and the thrust of liftoff. If you were to take a complete Saturn V system and magically teleport the whole thing stages and all into space and have it perform a re-entry, the capsule would have to jettison the entire rest of the rocket lest the stresses disintegrate the vast bulk and send the capsule section flying unpredictably and unstably towards a fiery doom.

In short the capsule was built a Hell of a lot stronger than the rest of the rocket combined as far as stresses are concerned. (Yes it wasn't necessarily materials strength, but rather design.)

Not quite. The Orion drive has a higher thrust to weight ratio than anything currently known. One bang and you go from zero to really damn fast really damn quick.

The problem with the Orion Drive being the amount of radiation it produces, which makes it a fairly poor choice for atmospheric work.

Again, here's how I handled it in my GURPS game:

Most starships have to stay the hell out of any kind of atmosphere because their first line of defense is shields that protect against impact but degrade a little with each interaction. Constantly having air molecules smash against them leads to unhappy shield generators, which in turn tends to lead to unhappy engineers, and trust me, you really want to keep your engineers happy. Ships can be deliberately designed to be atmosphere-capable with the addition of a plasma bubble generator which traps a mass of highly-energetic ions in an energy-field shell around your ship that gives you a nice, smooth deceleration from orbital velocity to safe airspeeds. Unfortunately, these things don't scale up very well, and about the largest they can realistically be built without sacrificing a lot of other functionality is about 100m, which is the typical size for heavy cargo lifters or the occasional planetary assault ship. It would technically be possible to build a larger vessel capable of entering an atmosphere by adding traditional heat-shielding and aerodynamic features to the hull, but nobody bothers with that because it's inefficient as hell (the one exception there is the Coalition, but nobody's entirely sure how they do it).

Thrust is also a serious issue on inhabited worlds because you can't use a ship's main drive anywhere near a human population (unless you really want to get sued into oblivion, and probably shot down by traffic control, who typically display an utter lack of humor on such matters), or for that matter anything you don't want to glow in the dark. Most larger atmosphere-capable ships use multi-drive systems, with atmospheric engines designed to get them up to the stratosphere where they can then light off fusion torch boosters (add a tank of reaction mass to a fusion reactor, that's an FTB) to carry them the rest of the way into space where the main drive (a physics-cheating Reactionless Drive) won't cause as much of a mess. Smaller ships can get away with just two drives as their main engines are safe enough once you're up in the stratosphere. On worlds without an atmosphere (or those where a bit of extra radiation won't matter much), the main drive can be used safely enough but it's still considered impolite to use it for actual take-off or landing (and again, traffic control tends to respond to that kind of thing with subpoenas and missiles. Opinions are divided on which of these are more painful).

As a result, ships tend to be divided into vacuum-only and surface-to-orbit types. Commercial traffic tends to switch between the two at orbital ports, military units will usually carry their own dropships. The exception is small transports and courier vessels, which frequently are both able to handle an atmosphere and capable of interstellar travel (this is the weight class the usual adventuring party would travel in).

Tom; Except the Command capsule didn't need the rocket to make re-entry and in fact left it behind wary earlier in the launch. The capsule isn't actually all that strong so much as it used a simple layered steel based ablative shield. It didn't need to balance out fuel, thrust, structure of the rocket, and the need of a multi-thousand ton rocket to hold an exorbitant amount of controlled explosion. The capsule can use the gravity of the planet to help draw it in it doesn't have to accelerate anywhere as hard going back in as it did going out.

Then again, if the EM drive works and it's not a fluke or error, then we may have to throw everything we know about rocket science out the window anyhow.

Oh the EM drive leading to FTL. I am optimistic but cautious.

EM Driving working as advertised (or even able to improved upon once we figure out why it works) will probably be the most significant invention in human history, perhaps only beaten by electricity or the Printing Press. Maybe

edited 29th Apr '16 10:21:08 AM by Jasaiga

Which is precisely the point. The Command capsule was designed for the stresses of re-entry, the rest of the Saturn V was not.

There is no point to be made though. The command vehicle isn't really all that strong and used nothing more then common spaced layers of steel cells for an ablative heat shield and a parachute to slow its fall. By comparison it is a lot simpler then the rocket. Getting into the atmosphere is a lot easier then getting out. It didn't need to fire off a Saturn V's worth of fuel in multiple stages to come back down but it certainly did to be lofted up and out. The Saturn V was designed to stand the abuse of the lift off and heat from its engines and heating from air compression going up. By definition of what it does has to be strongly built. Flimsy rockets tend to not cut the mustard and have a habit of turning into fireballs before they get up high enough to matter. There is a reason outside of direct military projects form DARPA, NASA has been one of the leaders in adoption of new material science breakthroughs.

You can even see the amount of thrust and burn time it takes to not only loft the whole unit to orbit but leave earth orbit for the Saturn V rocket. The first stage alone is over 7.5 million lbs of thrust with a burn time of 168 seconds. The second stage is 1 million lbs of thrust with a burn time of 384 seconds. By the time the third orbital insertion stage kicks off the hard work has been done and it only needs a comparatively low 202 thousand lbs of thrust and a burn time of 147 seconds. All of that is just to get the payload to orbit so it can then depart the earth's orbit with a fourth burn stage.

When you talk about landing large war craft on a planet it would be a lot easier to get it down then get it back up. The amount of effort to land that kind of mass won't be small either and getting it back up would require an enormous amount of energy that makes all the energy and power of Saturn V look like a fire cracker next to a MOAB.

Realistically if you manage to land it you are very unlikely to get it back up again without an amazing amount of effort. Otherwise you need the softer sci-fi options.

I forgot about the Orion Drive, thanks Tom.

So I've been looking at some ideas for a setting of mine, it's After the End and all, and one of the most advanced points about it before everything went to shit was something called a Molecular Printer / Assembler. Works like any other 3D printer only it can print any non organic item from a set blueprint using raw materials. In setting they are rare and a sign of how advanced humanity was before everyone fucked everything up.

But now I'm wondering, what could one Molecular Printer do for logistics for a army? How could even a few radically affect humanity's use of technology and society?

Can it print another printer?