Ground Weapons VS Starships

[DFW]

Unless you factor in that the odds of a random impact are 1 per 150 years for a 1 gram object and 1 per 150,000 years for a 1 kg object.

And 10-40% of objects that impact will hit a fuel tank rather than a critical space

Really? Where did you get those odds?

If something with that much energy hits a tank, it doesn't matter as it's going all the way through unless, the hull is strong enough to stop it...

 

[atpollard]

If 10-45% of a ship by volume is jump fuel, then 10-40% of impacts will be to a fuel tank. One could use a hit location table to get a more accurate statistical distribution of impacts in a Traveller universe if one wished, but the odds of ANY impact are less than 1 in 150 years (and probably several orders of magnitude less) so WHERE an object doesn't hit is a fairly fine hair to split.

 

[DFW]

but the odds of ANY impact are less than 1 in 150 years (and probably several orders of magnitude less) so WHERE an object doesn't hit is a fairly fine hair to split.

I'll ask again; WHERE do you get that data from?

 

[atpollard]

If you were questioning the 1 per 150 year odds (your post was vauge), then the explanation was from the second post in "How strong is my Starship Hull"

Ok, just for fun I did the math and here are the results:

GIVEN:
density of space dust at 1,000,000 molecules per cubic meter of space
1 gram of hydrogen = 6 x 10^23 molecules

THEN:
There is 1 gram of interplanetary dust per 3 x 10^17 cubic meters of space

Let us assume that all of this dust is a single object weighing 1 gram (a bad assumption since the density of large objects is orders of magnitude lower than that of molecular dust but it gives us a starting point), then a spacecraft travelling between worlds will strike an average of 1 object weighing 1 gram per 3 x 10^17 cubic meters of swept volume (the frontal area of the ship times the length of the trip).

For purposes of this discussion, we will assume that a 1 gram object will pose a threat to the ship’s hull.

The good ship FRED, a 200 dTon merchant ship, has a frontal area of 200 square meters (a high estimate) and will travel 6 x 10^11 meters (600 million km) to a gas giant to refuel. Thus the volume of space swept by FRED is 1 x 10^14 cubic meters per trip. Dividing the 1 x 10^14 cu. m. by the 3 x 10^17 cu. m. yields a 1 in 3000 chance that the ship FRED will strike a 1 gram object on a trip to the Gas Giant.

If the good ship FRED makes this trip every 2 weeks, then it should strike a 1 gram object every 115 years.

If the hull of good ship FRED is only dinged by a 1 gram object and requires a 1 kg object to penetrate the hull, then the good ship FRED should strike one dangerous object every 115,000 years.

I must conclude that the danger from striking interplanetary objects has been greatly exaggerated and the need for super-impenetrable hulls has been overstated.

 

[DFW]

Ok, just for fun I did the math and here are the results:

Got it. So, it's not from actually evidence. BTW, perhaps tons enters Earth's atmosphere annually. Also, hitting something 1/10 of a gram would be the equivalent to being hit by that super gun listed earlier in the thread. So, your calcs aren't close to real life data.

http://en.wikipedia.org/wiki/Micrometeoroid

 

[Solomani666]

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Micrometerites and Starship Hull Strengths:


A few things that seem to be lacking from this debate:

1. Outside of an asteroid field what are the actual chances of a ship being struck by a micrometeorite?

2. What are the likely relative velocities and angle of impact?

3. Can ships detect micrometeorites, with say milimeter radar, and simply make a course correction to avoid the impact?

4. What is the relative 'hardness' and 'density' of the meteorite compared to the ships armour, since this factors greatly into whether the object will penetrate the ships hull or just crater it, releasing most of its energy as heat.

5. How much energy does it take to vaporize a certain amont of crystaliron or BSD?

Until the above questions are answered, simply calculating Joules of energy will leave no definate conclusion as to whether a micrometeorite will penetrate a ships hull or how strong a starship hulls needs to be to travel safely. [Personal statement omitted]


Note: All basic traveller hulls are armored to some degree. The hull armor rating is just added armor relative to a starships basic armor rating.

.

 

[barnest2]

5. How much energy does it take to vaporize a certain amont of crystaliron or BSD?

MGT certainly doens't have the answer too this, as we don't know anything about it's density I don't think.
There might be better answers in mega-traveller or other editions, but you won't find an answer in mongoose books.

 

[DFW]

.

1. Outside of an asteroid field what are the actual chances of a ship being struck by a micrometeorite?

According to MGT encounter charts, in an inhabited system, at least 1 in 36 per trip and up to same per hour.

2. What are the likely relative velocities and angle of impact?

That depends on space craft speed.

3. Can ships detect micrometeorites, with say milimeter radar, and simply make a course correction to avoid the impact?

If so, then the sensors are MANY orders of magnitude better than the ship design rules.

4. What is the relative 'hardness' and 'density' of the meteorite compared to the ships armour, since this factors greatly into whether the object will penetrate the ships hull or just crater it, releasing most of its energy as heat.

Based on known data, anything from rock to nickel/iron. Given the kinetic energy released, it is MUCH more than a star ship laser.

5. How much energy does it take to vaporize a certain amont of crystaliron or BSD?

See weapon damage in MGT rules.

Until the above questions are answered, simply calculating Joules of energy will leave no definate conclusion as to whether a micrometeorite will penetrate a ships hull or how strong a starship hulls needs to be to travel safely. [Personal statement omitted]

Done, to the degree needed to know that if you hit one during a long interplanetary journey, in a small ship, you are toast.

 

[barnest2]

Done, to the degree needed to know that if you hit one during a long interplanetary journey, in a small ship, you are toast.

Actually, a question. How small a ship are you talking DFW. Because up too a 100 ton ship even, a micrometeorite can do major damage including wrecking a ships hull...

 

[DFW]

Actually, a question. How small a ship are you talking DFW. Because up too a 100 ton ship even, a micrometeorite can do major damage including wrecking a ships hull...

You are correct. I'm talking about small star ships. Usually of the type operated by players.

What is funny is that on the tables, in an inhabited system, you can roll MANY times during an interplanetary trip with a 1/36 change (each roll) of striking one for 2D6 damage. A small craft <50 tons isn't going to last long. A 100 ton won't either. Can't imaging the insurance premiums charge for small ships. :lol:

 

[atpollard]

Ok, just for fun I did the math and here are the results:

Got it. So, it's not from actually evidence. BTW, perhaps tons enters Earth's atmosphere annually. Also, hitting something 1/10 of a gram would be the equivalent to being hit by that super gun listed earlier in the thread. So, your calcs aren't close to real life data.

http://en.wikipedia.org/wiki/Micrometeoroid

The density of dust is accurate, as is the assumed geometry of the trip to a gas giant.

The Earth has about 500,000,000,000 times the frontal area of a Fat Trader and will sweep a far greater path through the cosmic dust. It is 1,500,000,000,000,000,000 times as massive as the Fat Trader and will draw far more dust into its gravity well.

All your reference demonstrates is that a 600,000,000,000,000,000,000 dTon starship with a 100,000,000,000,000 square meter frontal area orbiting the sun is pretty much screwed if it cannot withstand micro-meteor impacts.

Let’s extrapolate the 20 thousand of tons of annual Earth impacts to a 400 dT starship with 200 square meters of frontal area travelling the same path as the Earth.

20,000,000 kg of dust/year x 200 square meters of frontal area / 100,000,000,000,000 square meter frontal area = 0.004 grams of dust impacts the ship per year. If a 1/10 gram dust fragment will damage the hull, then there the ship should experience a 0.1 gram impact every 25 years.

Of course the typical impact velocity (from your wikipedia source) is “kilometers per second” – far less than your proposed super-gun equivalent event, and a starship would not spend every hour of the year travelling at in high speed to and from the outer solar system. So halving the number of impacts (the ship travels only half of the time) and halving that again (many will be at too low a velocity) yields one dangerous event per 100 years.

The math disagrees with your opinion that dangerous impacts would be common (except for Death Stars).

 

[far-trader]

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1. Outside of an asteroid field what are the actual chances of a ship being struck by a micrometeorite?

According to MGT encounter charts, in an inhabited system, at least 1 in 36 per trip and up to same per hour.

You do know that isn't even close to realistic for known facts right? That it is just a "kewl rule" for "adventure" fun, because nothing spices up a boring evening of "You reach the 100d jump point and nothing happened." like "After a few minutes of thrusting as you run for the 100d jump point a loud explosion shakes the ship! You've hit (been hit by) a micrometeor and your maneuver drive is damaged!!" and the players have to make frantic repairs or be caught!!

And the odds of successfully navigating an asteroid field are...

...actually pretty decent, C3PO didn't know what he was talking about. You'd have to go out of your way, a long way out of your way, to hit an asteroid while flying through a belt. You'd have to take careful aim and do it on purpose.

 

[DFW]

cts the ship per year. If a 1/10 gram dust fragment will damage the hull, then there the ship should experience a 0.1 gram impact every 25 years.

Only if it wasn't making frequent interplanetary trips (distance involved)

Of course the typical impact velocity (from your wikipedia source) is “kilometers per second” – far less than your proposed super-gun equivalent event,

:lol: Umm, ADD the speed of the ship. Were you trying to make a joke?

 

[DFW]

You do know that isn't even close to realistic for known facts right? That it is just a "kewl rule" for "adventure"

Yes, I was just throwing that in for people who wanted to point out the rules as being logical.

 

[far-trader]

You do know that isn't even close to realistic for known facts right? That it is just a "kewl rule" for "adventure"

Yes, I was just throwing that in for people who wanted to point out the rules as being logical.

Good Just best to be clear that is the point being made

 

[DFW]

You do know that isn't even close to realistic for known facts right? That it is just a "kewl rule" for "adventure"

Yes, I was just throwing that in for people who wanted to point out the rules as being logical.

Good Just best to be clear that is the point being made

Yeah, I mean if you actually used the encounter charts you would be dead in no time and interplanetary travel would be a suicide mission.

 

[barnest2]

Out of interest...
How would a Mars mission survive the trip? Am I just being stupid?

 

[DFW]

Out of interest...
How would a Mars mission survive the trip? Am I just being stupid?

No, you're not being stupid. A current day Mars mission would take months as the crafts speed would be a tiny fraction of a what Traveller space ship travels (hours to Mars). So, not a big problem.

Think walking across the room and hitting a bullet suspended by a string vs. a rifle firing that bullet into you.

 

[rust]

Out of interest...
How would a Mars mission survive the trip? Am I just being stupid?

No, you are not. Besides, several of the deep space probes meanwhile
have travelled much further than Mars, and with almost no evidence of
being hit. However, they all travelled at comparatively low speeds. I
doubt that they would have suffered more damage at higher speeds,
but I cannot rule it out.

 

[DFW]

Besides, several of the deep space probes meanwhile
have travelled much further than Mars, and with almost no evidence of
being hit.

Actually, not true at all. There has been many encounters that have caused pitting and holes in the solar panels. It is just that the velocity is so low that it isn't a big deal unless they hit something several grams in size.