# Are asteroid collisions as dangerous as they seem?



## caters (Apr 11, 2017)

The generation ship in my fictional story was built by aliens that know how to use these 3 things:

Artificial gravity to make it feel like earth throughout the ship.
Controlled nuclear fusion with 6 tanks. Only 1 needs to be fueled and you have fuel that will last for at least thousands if not millions of years. Going at .5c(half the speed of light), this is no problem
Artificial magnetic field to protect from high energy gamma ray bursts while still letting visible light through

After they randomly select 5000 passengers that fit a certain set of criteria for being on board and in a 1:1 sex ratio with lots of genetic diversity, they use booster rockets that immediately detach once they are in space. They then use nuclear fusion. At half the speed of light, it takes them nearly 2 years to traverse the solar system. They arrive at Mars within minutes but all the planets from there take at least an hour to arrive at.

But there is 1 main danger when going from Mars to Jupiter. That is the asteroid belt. A similar danger arises when they reach Pluto and the Oort cloud, but in this case it is comets, not asteroids.

But there is 1 thing that puzzles me about the asteroid belt. Meteroids, some as small as a speck of dust, I have heard are more dangerous than asteroid collisions regardless of your speed.

I get 1 factor into why meteroids are more dangerous, they are much more common than asteroid collisions with a spacecraft would be. But if the aliens were able to travel to earth, they probably ran into both of these things. Thus they would have developed technology for their ship to withstand both of these things a lot before they went to earth.

So if the generation ship can withstand meteroids and asteroid collisions, meteroids would probably be as dangerous to them as a black hole is to us on earth, in other words, less than a 1% chance of them being dangerous, much less. 

Asteroid collisions in comparison are much more dangerous. Even though the ship is what takes most of the force of the collision, there would still be a lot of sudden force inflicted on both the aliens and the humans. Luckily, the aliens have a 2 thumbed hand with each thumb on the opposite side of their hand so their grip strength is much stronger than ours. If it breaks anything, it would likely be the eggs of which there can be 5-15 per clutch and there is 1 clutch every few years(yes, my reptilian aliens lactate).

Anyway, for the humans, this sudden force from an asteroid collision is dangerous. Even with a very strong grip, the human hand just can't take that much force without letting go of whatever it is holding on to. Thus there would literally be a pile of humans with fractures in all sorts of places and probably some bad burns(the generation ship has a metal surface that is heated to a comfortable temperature. Since metal conducts heat, all the force from humans falling and sliding due to an asteroid collision could cause blistering burns).

Obviously, my generation ship has a medical bay for this problem and more.

But is my reasoning right? Is an asteroid collision with a very fast spacecraft as dangerous as I think it is? Would it really cause fractures and burns from all that force? Would humans even survive the force of an asteroid collision?


----------



## Vaporo (Apr 12, 2017)

First of all, why are they trying to drag their great big cumbersome generation ship off of the surface of Earth? Wouldn't it make more sense to keep the mothership in space and send shuttles to collect people from the surface rather than wasting incomprehensible resources trying to land and relaunch something that I imagine is comparable in size to a skyscraper? 

_Asteroids are not a major threat to spacecraft._ The asteroid belt is sparse. The Oort cloud is even sparser. When you look at a diagram of all the asteroids in our solar system, it looks dense, but that's only because every asteroid has been scaled up to the size of Saturn to be visible on the diagram. The odds of a spacecraft colliding with an asteroid by accident are roughly akin to the odds of two motes of dust colliding in a manufacturing cleanroom. Plus, if your aliens have the technology to cross interstellar space, they'd probably also have the technology to detect asteroids and, in the one-in-a-billion chance that they were actually on a collision course, perform a tiny maneuver thousands of miles in advance to avoid it.

Micrometeoroids are a threat because they are too small to detect and too numerous to totally avoid even if they could be detected. Impacts from micrometeoroids can be mitigated by simply covering your ship in something that can absorb the impact. For your ship that's going to be going at half the speed of light, depending on what resources you aliens have available (presumably lots) you'd probably just want to cover the front of the thing in a three+ foot thick layer of solid steel. We don't really know how densely micrometeoroids populate interstellar space, but it's safe to assume that there's at least some. If your ship were to be hit at that speed, it wouldn't be very fun for anyone inside unless proper precautions were taken.

However, since you're asking, let's say that their guidance computer is drunk, nobody on board knows how to use the radar, and they've been cursed with incomprehensible misfortune and are actually on a collision course with a full-sized asteroid. Even if you're aliens had miraculous materials technology that would prevent their ship from being instantly vaporized, everyone on board would die. Unless they have magical physics-breaking technology that somehow distributes the impact to every particle of the ship at once, the acceleration would instantly turn everyone's innards to a thin soup. Getting burned by the ship's heating system would be the least of their worries.

Well... All right. If the asteroid were just the right size, then there could be a significant jolt that could injure the passengers without killing them. But that still means that this massive ship's structure is somehow able to take a massive hit without totally getting ripped apart. I suppose that if I were reading a book and this scene occurred, I could accept it and move on with the story if the technology presented were shown to be capable of this kind of thing, but not without at least a little bit of grumbling.

Also...



caters said:


> meteroids would probably be as dangerous to them as a black hole is to us on earth,



This... makes no sense whatsoever. Black holes are astronomical objects that occur only under the most extreme conditions. It's like saying "parasites are just as dangerous to rabbits as volcanoes are to twinkies."




caters said:


> The generation ship in my fictional story was built by aliens that know how to use these 3 things...
> 
> Artificial magnetic field to protect from high energy gamma ray bursts while still letting visible light through



Magnetic fields do not defend against gamma rays. At least, not without converting any unfortunate nearby humans into a stringy pulp first. They can defend against charged particles, but gamma rays are not charged particles. It's just easier to use normal metal foil radiation shielding. Plus, a gamma ray burst is an extraordinarily rare event, even rarer than asteroid collisions. In fact, it can literally only ever occur at most once per solar system. And only a few solar systems have stars that can possibly create gamma ray bursts.

I'll be blunt: it sounds like you've heard about these things on TV or on the internet, but you hadn't done any sort of research into them before you started to develop your story. I would HIGHLY recommend that you do more research before trying to write the kind of story that you seem to be trying to write. All you do by not doing your homework on this is alienate potential readers.


----------



## CupofJoe (Apr 12, 2017)

I don't think it is how the person [human or otherwise] deals with an the impact to them, but more to do with the ship they are in suddenly being torn open either by direct impact [sort of like the Titanic and the iceberg - but at very different speeds of course] or by decompression [like popping a balloon]. If your aliens have _Star Trek_ style deflector shields then you can _boldly go_ as much as you like. If you don't, then it might be more like the film _Gravity_.


----------



## elemtilas (Apr 12, 2017)

Vaporo said:


> All you do by not doing your homework on this is alienate potential readers.




Or at least those readers who know a lot about asteroids and gamma rays and so forth...

Anyway, I would imagine that if these people had such wonderful technologies, they could just harness one of those big old asteroids, hollow it out, build a biosphere inside, then send that winging through the galaxy. I should think that a hollowed out asteroid's carapace would be able to handle almost any kind of impact it's likely to encounter. Unless someone's trying to drive it straight into a planet.

An ordinary space ship --- the usual kind we Earth folk tend to imagine --- I think would not last long out there with no supply line and no hope of repair or spare parts apart from what they bring with them. With a planetoid sized space ship, you've got a lot of room for spare parts and heptupally redundant plumbing, electrical, navigational and life support systems.

Perhaps they could even send out generation asteroid-ships in pairs. Extra room that way. Plus you've got a life boat not too far away...

Agree about blasting a generation ship off from planetside --- with good rockets, we can just about manage shifting a ship little bigger than a Winnebago into space. A ship to hold 5000 people for thousands of years, plus the 5000 people is, I think, a bit of a stretch.


----------



## Vaporo (Apr 12, 2017)

elemtilas said:


> Or at least those readers who know a lot about asteroids and gamma rays and so forth...



Well, a story about fusion-powered generation ship traversing the blackness of space tends to attract readers who know about those things.


----------



## psychotick (Apr 12, 2017)

Hi Caters,

It sounds like you need to do some work on your basic tech / science. Few obvious issues. 

First your times to reach planets are way off. Assume they leave Earth. They aren't going reach Mars in a few minutes. If they were made of light, travelling at half the spead of light then yes - half an hour. But they aren't light. They're solid. And you can't just get in your ship and instantly be doing 1/2 c. So they have to accelerate. They aren't travelling at half light speed. But lets do a simple calculation. Say their ship can accelerate at 1G - which is incredibly fast I might add over an extended period of time. That equates to an acceleration of 9.8 meters per second per second. Lets round it up to 10 for convenience. The speed of light is roughly 330,000, kilometers per second. Simply division tells us that with that sort of acceleration it will take them 33,000,000 seconds to reach the speed of light, or a little over a year.

Next problem is that your planets aren't all lined up in a row. So say you hit Mars in a few weeks. Jupiter may be on the opposite side of the sun when you get there, Saturn to your right etc etc. Do they need to decelerate, stop, turn around and head the other way?

And last if you're trying to get to all these planets, they have to accelerate and decelerate for every stop. Think of it like a train. You don't just get off a train at fifty miles an hour at the station and then board it again the same way.

Next the magnetic thing. I suspect you are thinking of the Earth's magnetic field as a defence against solar radiation. Not really relevant to space ships. As was said before, think about shielding in terms of foil etc. Go look up the specs of the ISS.

Last your impacts. Your ship is unlikely to hit anything of any significant size. But the collisions that you're talking about, something that hits so hard it smashes the entire massive ship off its trajectory, aren't survivable. Forget the people flying around the room and breaking bones. Your ship wouldn't survive. At the very least it would be multiply holed, which means goodbye air.

Hope that helps,

Cheers, Greg.


----------



## plasticroyal (Apr 12, 2017)

I find the focus on the 'grip' power of the passengers really jarring and unnecessary. In a ship/comet collision scenario that really isn't going to play a role in the survival rate of passengers.

I agree with Vaporo completely, you need to do a lot more research on the subject. Even with my limited understanding of the mechanics of space flight I can see obvious holes and underdeveloped ideas. You'll be doing yourself and your work a disservice if you don't take more time to understand the realities of the ideas you're trying to implement here.


----------



## pmmg (Apr 12, 2017)

I agree with the comments above. Asteroids are not really close together, and should be easy to avoid by just turning the wheel a little. Though, I suspect the crew of the Titanic thought the same thing about icebergs, so stuff happens.


----------



## Russ (Apr 12, 2017)

caters said:


> Anyway, for the humans, this sudden force from an asteroid collision is dangerous. Even with a very strong grip, the human hand just can't take that much force without letting go of whatever it is holding on to. Thus there would literally be a pile of humans with fractures in all sorts of places and probably some bad burns(the generation ship has a metal surface that is heated to a comfortable temperature. Since metal conducts heat, all the force from humans falling and sliding due to an asteroid collision could cause blistering burns).



Seat belts man, seat belts.

Oh, and the whole thing about getting bounced around has to be modified because the folks are not in gravity, or by the type of artificial gravity you are positing.  I suspect your generation ship is going to need artificial gravity.

I am also bit confused about what the fact that metal conducting heat has to do with burns from friction or sliding.


----------



## skip.knox (Apr 12, 2017)

Are asteroid collisions as dangerous as they seem?

Yes.


----------



## caters (Apr 13, 2017)

Russ said:


> Seat belts man, seat belts.
> 
> Oh, and the whole thing about getting bounced around has to be modified because the folks are not in gravity, or by the type of artificial gravity you are positing.  I suspect your generation ship is going to need artificial gravity.
> 
> I am also bit confused about what the fact that metal conducting heat has to do with burns from friction or sliding.



It already has artificial gravity. Extreme force of a collision does not change the fact that they are in artificial gravity. And piles of humans with fractures does not necessarily mean that they are being bounced around. That would only be the case if the ship got a lot of force pushing it back or if there was an upward force from the asteroid.


----------



## plasticroyal (Apr 13, 2017)

caters said:


> And piles of humans with fractures does not necessarily mean that they are being bounced around. That would only be the case if the ship got a lot of force pushing it back or if there was an upward force from the asteroid.



I feel like you're relating this event too closely to a car crash on Earth. An asteroid wouldn't stop the ship in its tracks like an obstacle would a car. And while it's likely that any passengers that were free-standing during this event would go flying, the resulting fractures would be the least of their worries. Maybe focus on aspects such as loss of breathable air, artificial gravity and internal pressure.

I too am confused with the 'friction/heat' aspect of the original post. I don't understand why the entire interior of a spaceship would be coated metal heated to such a high temperature that contact would result in burns. I think your ideas need a bit of editing and a bit more research before they'll really come to life - but this is definitely something you can achieve


----------



## Russ (Apr 13, 2017)

caters said:


> It already has artificial gravity. Extreme force of a collision does not change the fact that they are in artificial gravity. And piles of humans with fractures does not necessarily mean that they are being bounced around. That would only be the case if the ship got a lot of force pushing it back or if there was an upward force from the asteroid.



Then what causes the fractures?


----------



## caters (Apr 13, 2017)

Isn't it obvious that the force from the asteroid is what causes the fractures, so 1 human is on top of another human and with that force bones get broken, especially the ribs in both humans and with a lot of humans trying to hold on despite the force, a lot of humans get fractures.

I mean gravity + friction is what causes fractures here on earth and it takes either a little force repeatedly(stress fracture from running for example) or a lot of force instantaneously(like falling from high up). Most greenstick fractures are either in children who's bones aren't completely ossified or in people that put a lot of repeated stress on their bones(long distance runners and sprinters are often affected by these fractures). These only need the treatment that would be used for a muscle injury, in other words, a lot of rest but not immobilization.

Most fractures though are not greenstick fractures and these fall into 2 categories based on position and 2 categories based on other joints.

The position categories are simple and compound. Most rib fractures, even pretty bad ones are simple because the intercostal muscles keep the ribs from causing pneumothorax or cardiac hemorrhage. Often, arm and leg fractures are compound but there are a lot of cases of simple fractures here as well.

The 2 categories based on joints are fracture and fracture-dislocation.

A fracture is considered just a fracture if no dislocation results from the fracture. It is considered a fracture-dislocation if the fracture causes a dislocation.


----------



## skip.knox (Apr 13, 2017)

I've lost what the question is. From the subject line, yes an asteroid collision would be catastrophic. Everyone would die. Not pile up in a corner; they would die. Put a force field around your ship and all problems are solved. But if the asteroid crashes through the hull, the whole ship is torn apart. And everyone dies. At which point, discussing the finer points of stress fractures seems rather beside the point, doesn't it?

Sorry, I'm simply not seeing what aspect of world building we're going for here.


----------



## Russ (Apr 13, 2017)

caters said:


> Isn't it obvious that the force from the asteroid is what causes the fractures, so 1 human is on top of another human and with that force bones get broken, especially the ribs in both humans and with a lot of humans trying to hold on despite the force, a lot of humans get fractures.
> 
> I mean gravity + friction is what causes fractures here on earth and it takes either a little force repeatedly(stress fracture from running for example) or a lot of force instantaneously(like falling from high up). Most greenstick fractures are either in children who's bones aren't completely ossified or in people that put a lot of repeated stress on their bones(long distance runners and sprinters are often affected by these fractures). These only need the treatment that would be used for a muscle injury, in other words, a lot of rest but not immobilization.
> 
> ...



Well, I know that you are apparently a medical student, but I can tell you with some confidence that friction has nothing to do with causing fractures, here on earth.  Friction causes burns.

Your knowledge of physics is also lacking.  The force of a asteroid hitting your generation ship would not cause the massive rash of fractures you suggest would occur any more than the force of a boulder hitting a train I was in would cause a mass of fractures to the passengers of the train.  It is the "bouncing around" that would cause fractures.

By the by, typing a whole bunch of stuff about different types of fractures does not illuminate the problem we are trying to discuss any more than me discussing compound comminuted open Colles fractures with bone loss followed by RSD helps demonstrate why your comments about friction are not accurate.

You're not trolling here are you?


----------



## psychotick (Apr 13, 2017)

Hi Caters,

No fractures are not caused by friction. They are caused by impacts. 

To illustrate, a long time ago in a city far away known as Dunedin, i on a twelve speed ran head first into the side of a car that abruptly decided to turn right and cut across in front of me. I remember little of the actual impact with the car, but will never forget the road. I suffered multiple rib fractures and a chin fracture from essentially belly flopping into the road on the other side - the impact snapped the bones. And massive friction burns along my forearms and the front of my thighs from then sliding along the asphelt.

Cheers, Greg.


----------



## ThinkerX (Apr 15, 2017)

At relativistic speeds (.5C in your case), even a micrometer the size of a dust mote will release energy comparable to an H-Bomb should it strike your spacecraft.  This is one of the major arguments against interstellar travel, right behind lugging enough fuel along for even a fusion drive spacecraft to attain those velocities.  In your case - rough guess - the fuel required would be equal in mass to a large asteroid.

That said, I did come up with a possible solution years ago:

Yes, a micro meteor strike at relativistic speeds will vaporize anything it hits - but that need not be the spacecraft itself.  I envisioned a paper thin 'shield,' kilometers in diameter, launched ahead of the spacecraft, with more launched as needed.  Micro meteors destroy those first.

Another big danger - for which you seem to have an unrealized solution - is gamma ray damage. This gets extremely ugly in the .5C range.  However, you are also lugging along a huge (asteroid sized) fuel mass.  That can act as a shield.  Hence, everything that matters (life, key electronics) is inside the 'fuel tank.'


----------



## Vaporo (Apr 15, 2017)

ThinkerX said:


> Another big danger - for which you seem to have an unrealized solution - is gamma ray damage. This gets extremely ugly in the .5C range.



Could you explain this one to me? How does increasing speed increase gamma radiation damage? Does the blue shift on incoming rays just make them much more dangerous than I think, or is there something else going on?

Also, I really think that this thread should be in "Research."


----------



## ThinkerX (Apr 15, 2017)

Vaporo said:


> Could you explain this one to me? How does increasing speed increase gamma radiation damage? Does the blue shift on incoming rays just make them much more dangerous than I think, or is there something else going on?
> 
> Also, I really think that this thread should be in "Research."



That works for the 'really quick answer.'  It also gets into the way the gamma rays will change the chemistry of the spacecraft and those on it over extended time at that velocity.  

Assuming the fuel challenge could be solved somehow, the papers I have seen usually claim a top speed for the spacecraft of 0.7 - 0.8 C, enough for 'time dilation' to kick in at very roughly 1.5 to 1.  These schemes typically involve very slow accelerations to reach that speed, something on the order of a year-plus for the more optimistic ones, ranging up to over a decade.  

For a straight fusion drive, the fuel requirements put the top speed at roughly 0.1 - 0.2 C - a journey of decades to reach even Alpha Centauri and most of a century to get to Tau Ceti.


----------



## Nomadica (May 12, 2017)

ThinkerX said:


> you are also lugging along a huge (asteroid sized) fuel mass.



How big is asteroid size?


----------



## pmmg (May 13, 2017)

I think skip says it best. If they het hit by an asteroid they die. End of story. 

But asteroids in the asteroid belt are not close to each other. They are millions of miles apart. The ship will not likely hit one. For smaller impacts give the ship a shield of some sort. 

I saw you included meteors. Meteors are not in space. In space they are just asteroids. They only become meteors when they hit an atmosphere and catch fire. Comets are the other moving body. 

I saw you said the aliens have two thumbs so they can hold on.  Errrr...no. If they get hit by an asteroid they die. There is no hilding on. Maybe, if they are really lucky they just get grazed by an asteroid, but even that is astronomically unlikely. Give the ship a shield or a good early warming mechanism and call it done.


----------

