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Old 02-15-2020, 12:19 PM   #1
DataPacRat
 
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Default Any GURPS stats for black holes, pulsars, etc?

I've got a statblock for a speedy little spaceship from 3e's Lensman, with protective shields of frankly absurd stats. I'm curious how closely it could approach a star's surface - or a solar flare, pulsar, black hole, or what-have-you. Has anyone got any way to calculate GURPS stats for such astronomical phenomena?


The shields in question:

* Meteor Shield. DF 1 vs matter. (DR 100, DR 10k vs explosions)

* Screens: Transparent to matter. Essentially transparent to low-energy radiation such as radio and visible light, while absorbing hard radiation such as x-ray and gamma.
- Outer screen. DF 3. (DR 500; DR 250k vs explosions, radiation PF 10^3)
- Middle screen. DF 5. (DR 2k; DR 4M vs explosions, radiation PF 10^5)
- Inner screen. DF 10. (DR 30k; DR 900M vs explosions, radiation PF 10^10)
- Wall shield. DF 20. (DR 30M; DR 900T vs explosions, radiation PF 10^20)

Total PF vs radiation: 10^38

(If the ship's Bergenholm inertialess generators are turned on, and the ship is free to move in response to a source of harm instead of being tractored up against a solid object, damage is reduced further; in the local area of a spiral arm of a galaxy, by a factor of 100.)
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Old 02-15-2020, 12:59 PM   #2
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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!
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Old 02-15-2020, 01:10 PM   #3
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by clu2415 View Post
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.


Quote:
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.


Quote:
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.)
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Old 02-15-2020, 01:49 PM   #4
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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.
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Old 02-15-2020, 02:01 PM   #5
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by Agemegos View Post
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.
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Old 02-15-2020, 02:20 PM   #6
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by DataPacRat View Post
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.
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Old 02-15-2020, 03:04 PM   #7
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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.
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Old 02-15-2020, 03:09 PM   #8
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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.
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Old 02-15-2020, 03:29 PM   #9
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Default Re: Any GURPS stats for black holes, pulsars, etc?

The black hole at the center of the galaxy isn't anywhere near solar size. It's a lot bigger than that.
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Old 02-15-2020, 03:31 PM   #10
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by doctorevilbrain View Post
The black hole at the center of the galaxy isn't anywhere near solar size. It's a lot bigger than that.
In EE Smith's universe it might not exist.
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