Any GURPS stats for black holes, pulsars, etc?

[clu2415]

Do you mean the tidal stresses from the gravity wells? A pulsar’s radiation emission? The radiation emitted by a black hole’s accretion disc?

Neutron stars (including pulsars) have a ridiculous magnetic field strength—and then there’s magnetars which are even higher! There could be an induction hazard from moving a metal object through that field. Neutron stars also have such intense gravity that they bend the light from their far side. You can observe 3/4 of their surface from one side!

[DataPacRat]

Originally Posted by clu2415

Do you mean the tidal stresses from the gravity wells? A pulsar’s radiation emission? The radiation emitted by a black hole’s accretion disc?

"Yes." :)

Anything potentially lethal to the ship's pilot Lensman, which can be reduced at least in part by the shields.

Neutron stars (including pulsars) have a ridiculous magnetic field strength—and then there’s magnetars which are even higher! There could be an induction hazard from moving a metal object through that field.

As an aside, in one of the Lensman novels, a speedster was built out of just about entirely non-ferrous materials, in order to minimize its detection signature for the setting's "electros". Of course, a sufficiently-strong magnetic field can warp the way electrons behave in ordinary matter, to the extent that you can levitate a frog in the right lab; and I'm pretty sure neutron stars can have much stronger magnetic fields than that.

Neutron stars also have such intense gravity that they bend the light from their far side. You can observe 3/4 of their surface from one side!

The version of the speedster I'm toying with can hit 324 Gs of acceleration, and can cancel 99% of what's felt with inertial compensators and artificial gravity, so could be able to get surprisingly close to a source of high gravity. (And that doesn't count being able to hit FTL when the Bergenholm generator is activated; as long as the ship's overall vector of momentum is pointed away from the mass, it should be able to escape.)

[Agemegos]

I don't think that's right. With the Bergenholm on your intrinsic velocity away from the gravitating mass ceases to have any effect, and all that matters is the resultant of vector addition of your thrust and gravity. A spaceship with inertia will in general orbit around a massive body, safely except for tidal strain. A free one will instantaneously acquire a superluminal velocity directly towards it. Go free wherethe gravity points towards a planet and you will near-instantly but harmlessly hit the ground. Do it where the gravity points towards a star or such and then, unless you are very quick to acquire some thrust, you will near-instantly contact its surface or come to a buoyant equilibrium within it, subject to terrible tidal strains and quiet possibly in a graviational field too strong for your motor to get you out of.

[DataPacRat]

Originally Posted by Agemegos

I don't think that's right. With the Bergenholm on your intrinsic velocity away from the gravitating mass ceases to have any effect, and all that matters is the resultant of vector addition of your thrust and gravity. A spaceship with inertia will in general orbit around a massive body, safely except for tidal strain. A free one will instantaneously acquire a superluminal velocity directly towards it. Go free wherethe gravity points towards a planet and you will near-instantly but harmlessly hit the ground. Do it where the gravity points towards a star or such and then, unless you are very quick to acquire some thrust, you will near-instantly contact its surface or come to a buoyant equilibrium within it, subject to terrible tidal strains and quiet possibly in a graviational field too strong for your motor to get you out of.

The latter situation is what I was trying to refer to. As long as the ship's maximum acceleration of 324 gravities is greater than the gravity exerted by the star/whatever, then the ship can point its overall acceleration away from the star and escape from it. But if it gets closer than, say, 2.78 AU to the 4,154,000-solar-mass black hole at the center of the galaxy, where the gravity is greater than the ship's thrust, then things get dicey. (At which point various sorts of Heroic Measures may be attempted to defeat the Cold Equations, such as throwing furniture out the airlock, looking for any other ships similarly trapped to investigate, etc.)

Of course, that's only dealing with gravity - I don't know any rules-of-thumb for such bodies' radiation, magnetic, or other characteristics.

[Agemegos]

Originally Posted by DataPacRat

Of course, that's only dealing with gravity - I don't know any rules-of-thumb for such bodies' radiation, magnetic, or other characteristics.

The radiation is repulsive, and less intense than a weapon, so the shields will deal with it. No problem. Just put up the shields and turn on the Bergenholm and the worst radiation can do is bat you away.

Any gravitational field stronger than the 324 gees of drive is a trap, though. If you are quick you can turn off the Bergenholm and blast laterally as hard as the passengers can take while inert: Sir Ike will prevent a collision so long as you have angular momentum, and any fall in will turn into falling out after periapsis.

Tides I'm not sure about. I think that maybe tidal strain can't affect you if you're free. That might leave you "damned if you do and damned if you don't" when it comes to the gravitational fields of nearby massive objects.

[AlexanderHowl]

In general, there is not much you can do about black hopes except stay far away from them. The energy released by the workings of the accretion disk is around 50%, so a 10 Sol-mass black hole surrounded by a 1 Sol-mass accretion disk that will last 1 billion years will release an average of 1,000 times as much energy as Sol, all in hard gamma rays. At 1 AU, that roughly translates to over 100,000 rads per second (if I am doing the math right), meaning that you would need a PF of 10,000,000 to survive for an appreciable amount of time. At 0.1 AU, it is 10 million rads per second. At 0.01 AU, it is 1 billion rads per second.

[Agemegos]

The shields on spaceships in the Lensman universe make them immune to weapons with beams far more intense than that. The wall-shields on a speedster cope easily with particles of dust and molecules of interstellar gas impacting at 120 parsecs per hour.

[doctorevilbrain]

The black hole at the center of the galaxy isn't anywhere near solar size. It's a lot bigger than that.

[DataPacRat]

Originally Posted by Agemegos

The radiation is repulsive, and less intense than a weapon

I'm wondering at what point that detail no longer holds true - where the radiation becomes stronger than, say, five hundred thousand d6 damage per second.

Originally Posted by Agemegos

The shields on spaceships in the Lensman universe make them immune to weapons with beams far more intense than that. The wall-shields on a speedster cope easily with particles of dust and molecules of interstellar gas impacting at 120 parsecs per hour.

That might be more due to the physics of the Bergenholm generator than purely the shields. Such a generator produces a field with a particular volume, and presumably shape; Doc Smith didn't go into the details, but it's plausible that the field is shaped to extend in front of a ship, far enough to 'catch' potentially-hazardous particles and render them at least partially inertialess before those particles impact the shields. (GURPS Lensman mentions that it takes a certain number of milliseconds for an inertialess field to fully form, but I'm not sure if that can be extrapolated to figure out how much time it would take to de-inertia-ize a random dust grain.)


I've been eyeing 4e's Spaceships 5, page 40, which contains a table describing how much dDmg a STL ship takes from ablative dust-grains. However, that damage appears to scale with the Lorentz factor of how fast the ship is going, which kind of breaks down when an FTL drive is in play. Still, it gives some potentially useful numbers. At 0.9c, the Lorentz factor is 2.294, and a ship suffers 48 dDR per year. (Or 48*3d=144d6 dDmg, if dDR runs out.) That would mean that at Lorentz 100, at 0.99995c, a ship would ablate 4,000 dDR per year (or 12,000d6 dDmg, or 120k d6 dmg per year, or about 48 dmg per hour). I just might be able to work up some further numbers for denser-medium relativistic impacts based on that.

I seem to recall some mention that damage-scales were tweaked between GURPS 3e and 4e, something about squares versus cubes. Does anyone know what the factor of change (if any) was?

[Agemegos]

Originally Posted by DataPacRat

I'm wondering at what point that detail no longer holds true - where the radiation becomes stronger than, say, five hundred thousand d6 damage per second.

Let's see. 120 parsecs per hour is 4.22 × 10^14 metres per second, and the interstellar medium is around 50 000 000 molecules per cubic metre. Divide by Avogadro's number. Molar mass of hydrogen is two grams. 0.000 07 kg/m²/s. ½mv² = 6.23 × 10^24 watts per square metre. Frontal area of a speedster would be a bit over six square metres. Call that, say, four by ten to the twenty-fifth power joules per second.

Spaceships beam damage table. Treat as a neutral particle beam. Four by ten to the nineteenth MJ. Nineteen powers of ten from 3 MJ => nineteen doublings from 3 dice decadal damage. Three million d6 of damage going "dink!" every second.

That might be more due to the physics of the Bergenholm generator than purely the shields.

Maybe. I have an idea that I remember reading about matter impacting the wall-shields and being smashed, besides imposing a drag, and not about it being turned free outside the wall-shield. But I'm not about to hunt the reference down.