space ship catching fire?/

Depends a great deal on your ship. Is it carrying flammable materials? Fuel? Is its power system the sort that would explode with an impact like that? Work out the details concerning your ship and then you'll have a better idea of what would happen to it if it crashed.

As for a titanium sword....I'm no metallurgy expert, but I don't see why not...

A spaceship crashing would only ignite on the basis of its own contained oxygen supply, unless the planetary atmosphere also contained oxygen. Which it could not, unless it had a biology capable of producing oxygen. One of the great, and scientifically stupid, myths of SF is the discovery of a life-devoid planet having an atmosphere containing breatheable oxygen.

Not. Possible. Oxygen is an extremely reactive element, present in Earth's atmosphere only because of its continuous renewal through photosynthesis in plants.

Lacking oxygen, no fire. Fire is nothing more than the energy release inherent in rapid oxidation reactions. Saturn's moon Titan has an atmosphere rich in methane, but you couldn't light a match there; nothing for the methane to react with.

So, to come full circle, a spaceship crashing might ignite its contained materials and contained oxygen, but once those chemicals were consumed, it would lie there in a physically flattened mess, but little more.

caw

If the planet has significant atmosphere of any gas, regardless of whether it has oxygen or not, a space ship coming into the atmosphere at high speed (as they do in Earth's atmosphere) such as from orbit will have a heat shield the way many re-entry vehicles do, or ceramic foam tiles like the Space Shuttle to absorb and deflect the heat due to re-entry. If it's not oriented right, or has damaged heat shielding (like Columbia did), it can "burn up" on reentry. This isn't the usual catching fire and consuming oxygen, it's the heating up due to friction with the atmosphere from going into it at such a high speed. If that happens, it'll surely crash land, but it won't matter by then. It'll probably come down like Columbia, in pieces.

As for a titanium sword, well, I know enough about metallurgy to be dangerous. Firstly, an alloy (made of the correct proportions of the correct elements) is stronger than a pure metal, so it would be made mostly of titanium mixed with whatever makes it stronger. But I suppose that's not important unless you're going to describe its manufacturing. Next, the important part: it can't be made the same way steel swords are made. Titanium melts at a much higher temperature than iron or steel, and so needs more advanced methods to work it, but if this is the same civilization that's flying space ships, that's not a problem.

benbradley said:

If the planet has significant atmosphere of any gas, regardless of whether it has oxygen or not, a space ship coming into the atmosphere at high speed (as they do in Earth's atmosphere) such as from orbit will have a heat shield the way many re-entry vehicles do, or ceramic foam tiles like the Space Shuttle to absorb and deflect the heat due to re-entry.

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Well, not necessarily. It's entirely possible said spaceship was not designed for re-entry; I don't imagine the Death Star would have much in the way of a heat shield . In which case it's probably just going to disintegrate entirely on re-entry.

I really don't know enough by way of scientific fact (the others who've posted here have provided ample info in that department already), but I find it hard to believe that a common reaction to a crashing ship would be for it to burst into flame. Even cars, which carry petrol, almost never burst into flame when they crash. My father is a firefighter and had been to a crazy number of horrific car accidents. I have no doubt that you can paint a heartwrenching picture of a starship's crash and aftermath without the use of fire. Just have it crash to the ground.

/end tired midnight rambling

Spaceship crashing into planet: implausable. Unless the planet has absolutely NO atmosphere, chances are excellent the spacship will catch fire before it reaches the surface. But then, only bits and pieces ever reach the surface. Think SST Columbia, February 1, 2003. And anyway, the planet's atmosphere would need to contain one of the products of combustion (ie: oxygen) for a fire to be sustained.

Titanium sword: My initial impression is that regardless of the metalurgy, titanium is way too light to be effective as a sword. Maybe a fencing foil, or dagger, or other stabbing weapon...not a sword. However, take a look at this article in Sword Forum magazine.

Offhand, I'd say titanium by itself isn't good for a whole blade. Not very hardenable. Some titanium alloy edge coatings can be very hard, but for the main body of the blade, it's hard to beat good spring steel. (Of course, with advances in ceramics and other materials, who knows what'll be available in the future.)

As for your spaceship, there are just so many variables. What kind of spaceship is it? Does the planet even have an atmosphere, and what kind? Is the spaceship partially steerable (rockets, control surfaces or other means) or just entering the atmosphere as a ballistic projectile -- and if so, at what angle?

Just remembered something I read a while back - how about a meteorite sword?

bkwriter said:

I have a space ship crashing onto a planet. Wouldn't the ship catch fire? Do I have it burn up or simply just crash onto the ground?

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Depends on your world pretty much. Usually a spaceship entering an athmosphere should burn up upon reentry, since it will be designed for vacuum flight, not athmospheric reentry. Using shuttles for that makes much more sense, since the environments are so different.
So, a spaceship not designed for reentry, falling through an athmosphere at a a high velocity will most likely burn. If it's a really big and dense ship, maybe some kind of heavily armored warship, it's imaginable that it'd only lose delicate equipment on the outside, but reach the ground more or less intact. Surviving the crash is another matter. Even surviving in gravity is another mater, since spaceships are not necessarily designed to survive that. Especially if the main axix of gravity is different from the main axix of thrust. Just like one of todays rockets would break if you were to lay it sideways, since it's designed to only survive g forces along on axis.

2. What do you think of a titanium sword?

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Not a good idea. Titanium is not actually harder than steel, and it is only stronger per weight, not per volume basis. For a sword, which has a pretty much fixed volume based on it's purpose, but doesn't need to be as light as at all possible (there can even be such a thing as a sword that's too light) titanium is a bad choice. The sword will be softer than iron (or rather: properly treated steel), and also break more easily. If you're looking for a sci-fi material to make a sword out of, ceramics are a much more interesting choice. Well already have some that are durable enough to make kitchen knives that don't shatter when dropped, and it's quite imaginable that it's possible to have ceramics that aren't too brittle to use for a sword. And it's a material that can be much harder than steel. Heck, you could probably have ceramics that are brittle, but so hard that it's impossible to break them by "just" using them for a sword. You might want a metal core though, to get a decent weight.
Unless you only intend to fight unarmored opponents, in which case a really light sword in a rapier design could work. Though ceramics are also really stiff, so they'll not be able to bend elastically, as steel can.

Lemme flesh this out a bit.

The Spaceship crashing onto a planet. This can range from "We're out of fuel and in two hours, we will impact the planet" to "the jets rumbled to a stop, and the ship plummeted 100 feet to the ground" to "The jets stopped, but with a rotten snal, the landing legs gave way, and the rocket crashed to the ground"

Depending on your scenario, your fire risk varies. Fire can come about through a couple of mechanisms: your fuel and oxidizer can start the fire. The hot pieces of your heat shield/melted parts can ignite ground cover, or even the metal of your ship can begin burning in the atmosphere, especially if it has magnesium in it. Incidentally, Titanium, a common spaceship building material, will burn in pure nitrogen.

Then there is the momentum aspect. If you have a very massive spaceship, or it is moving very quickly with respect to the planet, you have a very large change in momentum once it hits the ground. In a small enough volume, it can generate enough heat to initiate combustion either of itself, or the surrounding environment.

As for requiring oxygen to have a flame, I respectfully disagree. An chlorine atmosphere is equally reactive. A jet of hydrogen in chlorine will result in a flame. Florine, too. Of course, somehow these highly reactive elements have to be renewed in the atmosphere, just like oxygen.

A sword does not have to be heavy to be effective. It's a matter of momentum. For example, baseball players are always trying to figure out how to lighten their bats, so they can swing them faster. It would make sense that the same hold true for swords. Now, a lighter sword can be beaten out of the way easier, so there's bound to be some drawbacks. But, not being a SCA sword guy, I really don't have a clue.

It would be much better to make a sword out of carbon nanofibers (or an entirely synthetic metal). There are a lot of other alternatives though if you look up modern metals on wikipedia, specifically under body armors and stuff. Kevlar, maybe.

BillPatt said:

Incidentally, Titanium, a common spaceship building material, will burn in pure nitrogen.

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That's an excellent point, and something I haven't thought of in ages.

A sword does not have to be heavy to be effective.

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A very light sword could also make up for its lack of heft by being extremely sharp.

Titanium will only burn if you get through the oxide layer first

Of course, there was that time on Xeelbob XII when the spaceship ferrying tons of oily rags slammed into that other spaceship carrying oxygen in low orbit.

Those muthas burnt all the way down and for a good time afterwards.

Well, "good time" being questionable ... The primitive locals, the anaerobic squid people of Xeelbob XII just sort of stood around and stared, glumly, it was like a dull party where no one danced, it was: Dude, shouldn't somebody call the Fire Dept. and the other guys were, What do you mean "fire" ???

Their Scientists couldn't really get a handle on it because of the issue of non-repeatability of the experiment; so they settled on starting a new religion over it. But all they pulled out of the fire was a piece of oily rag and the oily rag has just sat there for four thousand years and won't burn.

One time a missionary ship arrived from Earth, and the ship's priest tried to explain that if the squids kept worshipping their scrap of oily rag, they'd be heathens, and go to Hell when they died. And the squids were all "Hell is an eternity of FIRE?" and the priest was "Yes! Yes!" and the squids were "Well, that's our fondest aspiration, we would like to spend eternity being one with the fire ... because actually this scrap of rag has been pretty disappointing for the last four thousand years. Hell, you say? That'd bring us closer to G-d, and it'd be so nice to finally see something burn."

On Earth, they tell their spaceship priests not to try to convert the alien races, just let them have their own holiness their own way ... and that's basically why.

I think to clear up a lot of the confusion in this thread we have to stop equivocating "burn up" and "burn".

Burning, as in oxidizing, will only happen to a spaceship if it crashes on a planet with an oxidizing atmosphere. On a planet with oxygen breathing life that can obviously happen, on dead planets it's somewhat less likely, since oxidizing molecules will react and become stable unless there's not enough reducing molecules around to react with all, or there's some mechanism that separates the compounds. Volcanoes are an example. In other words, crashing on a planet like earth, or like Venus, a spaceship might catch fire and burn, provided there's enough flammable material on board and open to the atmosphere. Not unlikely, since a flame retardant outside ist not usually required for a vessel travelling through vacuum. Also, since given enough heat, even aluminium or steel are flammable.

Which brings me to "burn up". If the spaceship enters an atmosphere -any atmosphere- fast enough, friction heat will destroy it. How fast "fast enough" (too fast, if you ask the passengers) is, depends mostly on the spaceship, and to a lesser extent on the atmospheric density. A spaceship would normally not be designed to travel through an atmosphere. The design of a vessel intended to travel through vacuum and free-fall for extended periods of time is so vastly different from the design of a vessel intended to enter and exit a planetary gravity and an atmosphere that it makes no sense to design a vessel that can do both. You don't build a submacopter. So, unless there is a very concentration of bolognium in the world available, say, dirt cheap energy to power magical shields and fantastical antigravity devices to make the atmosphere harmless and the gravity irrelevant, you'll have spaceship designed for deep space voyages, and shuttles for re-entry and take-off from a planet. Which means the spaceship, not being designed for landing on a planet will probably "burn up" in the atmosphere, i.e. be destroyed by the air friction and the heat generated by the friction. The spaceship will not be aerodynamic (being designed to flying where there is no air) thus have lots of frilly bits (radiators, sensors, steering thrusters and the like) which will generate lots of air friction, and, not being protected against friction heat, melt and vaporize. Depending on just how flimsy the spaceship material is, and obviously on how fast the re-entry, anything could happen from most fragile outer parts being burned off to the whole spaceship arriving as a clump of half-molten slag. Provided the spaceship is heat resistant (unlikely, since it'll be designed to operate in a perfectly vacuum-isolated and cold, make that COLD, environment) it could still break up because of the shocks caused by air turbulences. Not being aerodynamic, there will be shocks.
If it descends very, very, slowly it might reach the ground intact, though that requires powerful, and working, engines. Assuming the spaceship reaches the ground intact, there is still the very real possibility of it simply being crushed by gravity. A spaceship will be designed to withstand acceleration only in the direction of it's engines thrust, so unless it somehow manages to land in a way that points those engines straight down, the gravity of the planet will point in the wrong direction. Imagine flipping a house on the side, it's not going to stay house-shaped for long since the weight no rests sideways on the load bearing structures (aka walls) which are not designed to hold it that way. Not to mention that even if it doesn't break completely apart, since it's not designed to rest under gravity on a surface, the -now- lower part of the spaceship will still get crushed by the weight, until it's flat enough that the weight of the upper parts can't compact the lower parts any further. All of this again presumes no magic of course.
A spaceship might make it to the ground intact if it was designed for some purpose which accidentally works to its benefit. I.e. a really sturdy spaceship, for example a heavily reinforced and armoured warship, or a ship designed to enter a gas giant and mine deuterium at high atmospheric pressures, might survive entering an atmosphere (it's not actually atmospheric re-entry if didn't start from the planet, is it?) and the uncontrolled flight into terrain. Acceleration at the wrong angle might still be a problem for the internal structures though.

Ah, didn't see this at first.

BillPatt said:

A sword does not have to be heavy to be effective. It's a matter of momentum. For example, baseball players are always trying to figure out how to lighten their bats, so they can swing them faster. It would make sense that the same hold true for swords. Now, a lighter sword can be beaten out of the way easier, so there's bound to be some drawbacks. But, not being a SCA sword guy, I really don't have a clue.

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Momentum is the product of mass and velocity. Trading mass for speed does not necessarily increase momentum. Especially not in the case of swords, where there is an upper limit to what speeds you'll get, and reducing mass will soon give you diminishing returns. Also, momentum is not the only relevant metric when considering the effectiveness of a sword, because even two impacts with the same momentum will have different effects depending on the mass and speed distribution. An easy example is shooting a tin can with a gun, compared to throwing a rock at it, which is ten times as heavy as the bullet, but only one-tenth as fast.

Lhun said:

Trading mass for speed does not necessarily increase momentum.

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I should have put in there that in a game like baseball, having a lighter bat means you can swing it around to the ball faster. It negates, to a degree, the advantage a fastball pitcher has. That is the main reason they go for a light bat - faster speed to get to the ball. Momentum is a secondary consideration.

It seems to me that a lighter sword will let you get the blade up to block, or to slice out that jugular just thaaat much faster than that five foot tongue of osmium. But if it gets too light, then the other guy just smacks it out of the way and does you in.

Good dissertation on your burn vs burn up post. Common usage of the verb "burn" does imply oxidation. Some rerduction reactions generate flames and smoke as well, and most laymen would call that burning, as well.

1. It will create friction that resembles a burning effect when travelling through the atmosphere. If the planet has a dense enough atmosphere anyway.
Fire needs oxygen to burn, so if the inside of a ship caches fire, venting the atmosphere in that area will kill it.

2. Short answer: Pure titanium is a no-no. But an alloy of steel and titanium could prove very useful indeed.

Long Answer: Depends really.
If a culture can produce titanium, odds are they would have other weapons that render such a close-range weapon as a sword defunct.
It's not a metal that can be forged by a race without much technology. The metal will actually burn before it reaches its melting point. You need an oxygen free environment to forge it.
Be careful if taking it out of an oxygen-rich area, if you do, the ductibility of the metal greatly increases, meaning it will warp much more easily.
Titanium's hype makes it seem superior at first. But when concerning cutting power, steel is still superior to titanium. An effective titanium blade would have to ber around the size of Cloud Strife's weapon to be effective. While a blade fo such size would still be light, the sheer size makes wielding it impractical. A steel blade would be far smaller than a titanium blade and still possess more cutting power. Steel can easily inflict damage on titanium.

I thought, rather than start a brand new thread for my question(s) along a similar vein, I'd add my questions to this thread and see if I got any responses. . .

Here's the scenario: a small ground-to-space shuttle is in a low orbit when it hits a space mine and is basically disabled. In a low orbit, I believe without engines keeping it on coure, the orbit would "decay" and send the shuttle and the pilot hurtling into the planet. Is that correct? What is the most believable way to have the pilot/ MC survive planetary impact? I'm thinking even a "spaceplane" or shuttle type ship wouldn't be able to survive with its engines/ thrusters and one wing badly damaged. Like the sad incident of the Columbia, a few years back, it would probably break up and "burn up" in the atmosphere due to friction, etc. If the shuttle's cockpit doubled as an ejection or escape pod, would it have an autopilot capability that could land it safely--as the pilot at some point gets knocked unconscious? Also, how long would it take a ship to fall from orbit to the planet? And how bad would the G-forces be on the MC?

I'm having the worst time doing this scene . . . I think my muse is reminding me of all the BAD sci fi movie spaceship-crashing scenes I've seen, like that dumb one in Star Wars III where Anakin lands this flaming hulk of a battle cruiser, and isn't reduced to a puddle of bloody goo by the end. Does anyone know of any books or movies that show a more realistic example of a crash?

Pepper said:

I really don't know enough by way of scientific fact (the others who've posted here have provided ample info in that department already), but I find it hard to believe that a common reaction to a crashing ship would be for it to burst into flame. Even cars, which carry petrol, almost never burst into flame when they crash. My father is a firefighter and had been to a crazy number of horrific car accidents. I have no doubt that you can paint a heartwrenching picture of a starship's crash and aftermath without the use of fire. Just have it crash to the ground.

/end tired midnight rambling

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Cars don't fall through the atmosphere for hundreds of feet, coming in at over terminal velocity. The worst car crash outisde of Nascar would involve cars travelling at about a hundred miles per hour. Spaceships travel much faster than that, and it's the atmospheric friction that does the burning, not the crash itself.

If your story is set far enough in the future (like not this October, but oh, a couple of decades hence, at least), there might be some sort of "escape pod" technology that would 1) allow the vehicle to withstand atmospheric entry (the reall killer, not the landing) and 2) keep occupants safe regardless.

What burned up the Columbia was the heat due to friction (as mentioned by Thomas above) that penetrated a tiny hole in the heat shield tiles on one wing. The damage your planet to low orbit shuttle sustains from an exploding mine would be significantly worse. If the pilot was conscious, he would consider himself toast. He might try to call for rescue, if such a thing was available.

It would take some time for the orbit of an object without thrust capabilities to finally decay enough that atmospheric friction grabbed it. Look up how long it took MIR or the Space Lab to wind up in the drink. The Columbia was already well into the atmosphere by the time the fire disabled it. Your character might have several months to a year or more to think about his inevitable demise.