Are asteroid collisions as dangerous as they seem?

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...

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."

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.

 

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.

 

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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

 

Then what causes the fractures?

 

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?

 

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.

 

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.'

 

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.