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Old 02-17-2020, 12:39 AM   #31
Johnny1A.2
 
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by whswhs View Post
The trick with inertialessness is that collision with a particle never inflicts damage. You just stop dead in space.
Not if your drives are firing, then it's a contest of the power of the drive vs. the friction with the medium. Ditto the influence of gravity or other forces.

(Though Smith did screw up his own imaginary physics badly on this very point in Vortex Blaster.)

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So what you have to be doing with those fields is not blocking out damage, but shoving the particles to the side so that you can move forward.
Exactly how that works is not clear. The ship has no momentum, so it has to be the structural strength of the ship transmitting the force of the drive to the particles.
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Old 02-17-2020, 09:30 AM   #32
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by Johnny1A.2 View Post
Not if your drives are firing, then it's a contest of the power of the drive vs. the friction with the medium. Ditto the influence of gravity or other forces.

(Though Smith did screw up his own imaginary physics badly on this very point in Vortex Blaster.)
Do you have more info on what he did wrong in there? (I'll admit that when I last read it, I was focused more on trying to extrapolate and fill-in Vegian society than on looking for physics exploits.)


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Exactly how that works is not clear. The ship has no momentum, so it has to be the structural strength of the ship transmitting the force of the drive to the particles.
It might be less the ship's structure and more the shields.

In a major battle in Second-Stage Lensman, we're informed that nega-matter responds to gravity the opposite way that normal matter does; and we're also told that shields pull nega-matter projectiles in towards the shielded ship, implying that shields exert a pushing force on regular matter. Ships of this era, including the speedster with the 30M wall-shield, also often have a couple of tractor and pressor beams, so it might be safe to model the ship's effect on interstellar dust particles as just shoving them to the side before they actually impact its structure.



Has anyone got any suggestions on how to convert the local temperature of space into damage?

The earlier suggestion of converting space-dust into the equivalent of a neutral particle beam worked out well; are there any rules-of-thumb to say things like "If you're close enough to a star that things get heated up to a temperature of 8,000 Kelvins, that's dumping X gigajoules of energy into your shields per turn, which can be treated like a laser doing Y damage per turn"? (If surface area matters, the speedster is 216 feet long and 12 feet in diameter, implying an area of around 8,400 sf.)
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Old 02-17-2020, 10:08 AM   #33
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Has anyone got any suggestions on how to convert the local temperature of space into damage?

The earlier suggestion of converting space-dust into the equivalent of a neutral particle beam worked out well; are there any rules-of-thumb to say things like "If you're close enough to a star that things get heated up to a temperature of 8,000 Kelvins, that's dumping X gigajoules of energy into your shields per turn, which can be treated like a laser doing Y damage per turn"? (If surface area matters, the speedster is 216 feet long and 12 feet in diameter, implying an area of around 8,400 sf.)
I think I've got a handle on damage from light/heat in terms of watts, if not Kelvins.

At 1 AU, the sun's output is 1,368 watts/m^2. At its surface, 0.00465 AU, that's about 63 MW/m^2. The speedster is around 780 m^2, so it's absorbing 49.3 GW of energy every second, or around 500 GW every 10-second turn. Spaceships beams of 300 or 1000 GW do an average of 5250 or 7000 non-decade damage, well within the shields' capacity.

One of the larger nearby stars, Vega, has a luminosity of 40.12 of the sun, or 55 kW/m^2 at 1 AU; at its surface (~2.5 solar radii, 0.0116 AU), 406 MW/m^2 every second; the speedster's surface absorbs 316 GJ per second, or 3 TJ per 10-second turn, a mere average damage of 10,500.

So far, so good; let's try some heavier stars, with the tables and formulae from GURPS Space.

A star of mass 10 suns has luminosity 11,000, temperature 20,000 K, radius 0.0406 AU, outputs 9.11 GW/m^2 at its surface, so the ship gets 71 TJ per turn, which if we round up to 100 TJ, implies an average damage per turn of on the order of 35,000.

A star of mass 100 suns has luminosity 110M, temperature 50,000 K, radius 0.65 AU, outputs 356 GW/m^2 at its surface, the ship getting 2.8 PJ per turn, enjoying around 105,000 damage per turn.


All in all, it looks like as long as the speedster stays outside of the star itself, it can handle the heat.

... So, anyone care to estimate the damage from going /into/ a star? :)
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Old 02-17-2020, 06:37 PM   #34
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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All in all, it looks like as long as the speedster stays outside of the star itself, it can handle the heat.

... So, anyone care to estimate the damage from going /into/ a star? :)
Found a possible starting point: 3e's Vehicles Expanion 1, and its formula for crush depth and test depth. Assuming that the wall shield pushes back against a star's matter, that it sticks close to the speedster's surface, and counts as an extra-heavy frame; and that every 11 yards of depth equates to a pressure of 14.5 psi; then the speedster's shield has a test depth that can handle a pressure of 234 gigapascals without a qualm, and a crush depth of 468 gigapascals.

What I haven't been able to find are any sources on pressures to be found inside a star, with one exception - that the centre of the sun is around 26,500 gigapascals. So at least we don't have to consider a speedster that can swim around throughout a star entirely unscathed. :)

The closest I've found to a depth-to-pressure chart is here, which is actually depth-to-density.


About the closest I've got to a plot-worthy result is something along the lines of "If you turn on a Bergenholm inertialess generator within a star's gravity well without turning on your drives, your ship is immediately drawn to its surface just as if the star had a tractor beam drawing you towards it. Your shields can resist the surface of the star's heat, light, and pressure for at least a couple of seconds, so make a skill roll to point your ship away from the star and turn on the drive before anything worse happens than the paint starts to singe..."
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Old 02-18-2020, 12:33 AM   #35
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by DataPacRat View Post
Do you have more info on what he did wrong in there? (I'll admit that when I last read it, I was focused more on trying to extrapolate and fill-in Vegian society than on looking for physics exploits.)
He describes a 'free' ship being driven backward (relative to the viewpoint character) by a single driving jet, specifically said to be doing this against the full force of the main drive.

That's not how it works anyplace else in the Lensverse. A 'free' ship with thrusters going in opposite directions will move (not accelerate, just move) in the direction opposite the stronger thrust. Going free won't let a 1 newton thruster overcome the effect of a 10 newton thruster...except that it does in that one instance.

Now, a single tiny thruster could _stop_ a free ship, if the main drive was off. For that matter, so can a single atom of hydrogen. But if _Dauntless_ has it's main drive starkly flaring at its prodigious maximum of thrust, a little retrothruster in the bow will not overcome that, whether free or inert.

Again, except in this one instance.
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Old 02-18-2020, 06:38 AM   #36
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by Johnny1A.2 View Post
if _Dauntless_ has its main drive starkly flaring at its prodigious maximum of thrust
Nicely worded :)
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Old 02-18-2020, 10:38 AM   #37
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Default Re: Any GURPS stats for black holes, pulsars, etc?

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Originally Posted by Johnny1A.2 View Post
He describes a 'free' ship being driven backward (relative to the viewpoint character) by a single driving jet, specifically said to be doing this against the full force of the main drive.

That's not how it works anyplace else in the Lensverse. A 'free' ship with thrusters going in opposite directions will move (not accelerate, just move) in the direction opposite the stronger thrust. Going free won't let a 1 newton thruster overcome the effect of a 10 newton thruster...except that it does in that one instance.

Now, a single tiny thruster could _stop_ a free ship, if the main drive was off. For that matter, so can a single atom of hydrogen. But if _Dauntless_ has it's main drive starkly flaring at its prodigious maximum of thrust, a little retrothruster in the bow will not overcome that, whether free or inert.

Again, except in this one instance.
Alright; I just found the moment in question, using the ship's main jets as a weapon against the Nhalian base. (Gotta love searchable ebooks.)

What would it take to rationalize this particular circumstance into the overall physics of the Lensman universe? For example, might it be feasible to say that the main drives can be tweaked to still put out a lot of heat (to melt the base) but not actually providing very much thrust? Could the fact that this manoeuvre was being done inside an atmosphere be turned to good use; maybe it could be claimed that an unmentioned detail in the novel was that the Bergenholms weren't turned on at full power, leaving enough of the ship's inertial physics in place to allow for such concepts as 'acceleration' to still have meaning?

I'll admit that I'm grasping at straws, but I'd really like to have all my Treknobabble lined up and ready to go. :)
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