Crashing ships as weapons

[Adam Dray]

Yeah, nobby-w. I've been assuming that a ship has sufficient shields to handle whatever dust it bangs into at whatever speed it is going. That's probably not realistic.

In any case, downthread we figured out that ships could never accelerate to near-lightspeed, anyway. It doesn't seem to matter, since a ship can accelerate to 0.3% c in a pretty short space at 5G, and 100 kg of ship moving at that speed is roughly equivalent to a Hiroshima-sized A-bomb.

 

[aramis]

Basically, all of special relativity, right? Of course, so does FTL travel outside of very specific instances of closed, timelike loops.

Violates GR, too. Which FTL does not...

 

[kilemall]

I really believe anyone who wants reactionless thrusters in their game should think about the above. It is inherently logical, uses real-world physics and would likely describe the way a real reactionless drive, should it ever be invented, would work in terms of power consumption.

I am a bit astonished this does not resonate more. (Not just because making that spreadsheet was fun... )

How about... don't wanna.

There is a certain freedom implied in the original CT movement rules that gave a feel of 'spaaaaaaace' without putting people on a hard no-choice calced maneuver.

I prioritize player choice over harsh physics, so I am more likely to create a new paradigm then be thrust mass/power restrained.

 

[kilemall]

As to the impact issue, went into that in my IMTU thread plus general discussions, including using repulsor tech for the small stuff.

Assuming we blow off all the accel issues, there would be a point at which maximum velocity would be determined by ship's ability to take small unavoidable damage, and how well the ship could evade damage by maneuver screening and/or fire.

The key to avoidance would be detection range of objects per size, and how much time that gives the ship to get out of the way. Obviously higher G ships could evade better, but at a certain point there will be no time to move.

Finally, the whole mass thing could be dealt with in a different way by reimagining gravitics.

Instead of 'pushing' or 'pulling', the grav drive could 'cut off' the ship's weight from the current spacetime, sort of like a classic warp field, and the whole ship is 'lighter' and pushed by reaction engines that require far less thrust to move the same ship.

 

[McPerth]

That's really interesting.

So call an Earthlike diameter 13,000 km. 1000 diameters is 13,000,000 km, or just 0.87 AU.

Anyone want to do the math to determine relative velocity attained at 5G in 13 million km? Check my math.

s = 1/2 ( a t^2 )
13,000,000 = (0.5) (5)(9.8 / 1000 m/km) t^2
t = sqrt(13,000,000 / 0.0245)
t = 23,035 seconds = 6.4 hours

vf - vi = a t, vi = 0
vf = a t
vf = 9.8 (m/s^2) * 23,035 s
vf = 1,128,715 m/s

c = 299,792,458 m/s

So final velocity = 0.3% the speed of light when the M-drive stops really adding to the velocity.

What I didn't do is the calculus required to account for the reduction of gravitic push as it diminishes from 100% at 0 diameters to 1% at 1000 diameters, as an inverse-square function of distance. That is, I assumed a constant 5G acceleration for the entire trip, which is not at all the case.

As you asked to check your numbers:

If I understand you well, the formula for final velocity is given as for 1 G, while you specified it was at 5 G. Yet, the final result is correct for 5 G.

 

[aramis]

Assuming we blow off all the accel issues, there would be a point at which maximum velocity would be determined by ship's ability to take small unavoidable damage, and how well the ship could evade damage by maneuver screening and/or fire.

Which said speed varies by direction of movement, size/type of star, distance from star, armor of ship...

... because...

• it's the relative velocity and particulate density that matters in determining the radiation damage from the alpha and beta - headed towards the star, relative speed to the star is reduced, as the particles are moving in opposition; moving away, subtracted.
• Distance reduces the particle density per unit cross section viainverse square.
• Nature and thickness of armor determine the interaction with alpha, beta and dust.

 

[Adam Dray]

Hey, debris collisions could be the science behind the maximum velocity thing. (Yeah, absolute velocity isn't a thing, I know.)

Do gravitics actually work better, the larger the ship is? G M m / r ^ 2, ne?

It'd be really interesting to see an enormous battlecruiser outperform (outmaneuver) a small fighter because it has stronger gravitic capabilities.

My Nova Roma setting deals with a lot of physics problems (e.g., relativity, causality, FTL: pick two) using a causality bubble like the one you describe. It creates its own inertial frame--essentially, a bubble universe--and then "jitters" it (handwave, handwave) by exploiting a "rounding error" in the universe's "code" and basically stutterwarps its way across known space that way. The faster it can jitter, the faster it can move. This travel is zero-inertia motion, meaning a ship can stop on a dime or just reverse or turn at weird angles. Since it's effectively not in this universe while it's englobed, it's seemingly invisible and impervious to attacks--except that it isn't: The jittering gives off a unique signature of Hawking radiation waves and the globe is vulnerable to powerful nuclear explosions.

 

[warwizard]

I still think we should rework the power required by any M-drive to be somewhat more than the amount of energy converted to velocity, after all no device is ever 100% efficient, Once that has been fixed, you simply point out that they do not have enough fuel to reach 10% of light speed by 2 or 3 orders of magnitude, due to power plant fuel requirements, unless of course they have antimatter.

 

[McPerth]

Do gravitics actually work better, the larger the ship is? G M m / r ^ 2, ne?

It'd be really interesting to see an enormous battlecruiser outperform (outmaneuver) a small fighter because it has stronger gravitic capabilities.

I've ver assumed (and just that, my assuming, I gues sto handwave many physics questions) that the fact mass is irrelevant for MD (I mostly played MT, where mass and tonnage were separated, but also applies to its performance on an empty/full ship) was due that increasing mass also increases the ship's own gravity (even if imperceptible), and that the gravitic MDs used this to work.

If I read you well, you seem to point this way too...

My Nova Roma setting deals with a lot of physics problems (e.g., relativity, causality, FTL: pick two) using a causality bubble like the one you describe. It creates its own inertial frame--essentially, a bubble universe--and then "jitters" it (handwave, handwave) by exploiting a "rounding error" in the universe's "code" and basically stutterwarps its way across known space that way. The faster it can jitter, the faster it can move. This travel is zero-inertia motion, meaning a ship can stop on a dime or just reverse or turn at weird angles. Since it's effectively not in this universe while it's englobed, it's seemingly invisible and impervious to attacks--except that it isn't: The jittering gives off a unique signature of Hawking radiation waves and the globe is vulnerable to powerful nuclear explosions.

That again reminds me Starfire game, that you already told me you didn't know...

 

[Adam Dray]

Nothing new under the sun, I suppose.

 

[Thot]

How about... don't wanna.

There is a certain freedom implied in the original CT movement rules that gave a feel of 'spaaaaaaace' without putting people on a hard no-choice calced maneuver.

I prioritize player choice over harsh physics, so I am more likely to create a new paradigm then be thrust mass/power restrained.

I don't understand - you don't want the laws of physics to apply to your game world? Then why bother with near-c-rock-issues at all?

 

[mike wightman]

A couple of questions have sprung to mind:

where did the 250MW=1EP come from other than a made up number in Striker - put another way is the output of fusion reactor in Traveller something we could redefine?

how big are the fission reactors used on subs and carriers today and what is their maximum energy output?

 

[Thot]

A US Nimitz class aircraft carrier (100,000 tons) has a power of around 200 MW. No numbers for the much more modern Ford class yet. A German Brandenburg-class frigate (4,900 tons) has diesel/gas power of 38 MW.

If I recall correctly, 250 MW per dton is given in MegaTraveller. Significantly increasing that number would break the universe, too.

 

[Lycanorukke]

how big are the fission reactors used on subs and carriers today and what is their maximum energy output?

From reading - the Ohio Class sub has a S8G reactor which generates about 220MW (thermal). The size is 13m diameter x 17m long, with a weight of roughly 2500 tons. Nimitz class has two A4W reactors rated at ~500 MW (thermal) each.

I can't find their electrical output, but civilian Nukes tend to have conversion effeciencies of about 30% for electrical power.

 

[Thot]

My numbers are from Wikipedia, but do only include propulsion power.

 

[Adam Dray]

Some googling suggests the Ford A1B plants produce 700 MW and 2.5x the electrical capacity of the Nimitz A4W.

 

[kilemall]

I don't understand - you don't want the laws of physics to apply to your game world? Then why bother with near-c-rock-issues at all?

Why have jump or any other FTL technology we cannot conceive of or reason ably extrapolate?

I'm approaching the game from entertainment first not physics lesson first. As part of that I like giving a 'hard space' feel but not go to your hardcore level.

As such I want to impart all the lethality implied in high velocity impacts in space (I have quite a corpus of posting on this aspect), but give the option of being able to zoom off somewhere without crippling constraints.

So as previously noted I want frac-C handling in defense of the Cities (humanity largely in Lagrange point Oneil stations), that means rocks or possibly a fine mesh, been juggling that in my head in light of solar winds/storms and stationkeeping.

I also have a need for near-C scout ships, so that will be enabled, period.

 

[Adam Dray]

I also have a need for near-C scout ships, so that will be enabled, period.

What drives that need?

 

[Thot]

Why have jump or any other FTL technology we cannot conceive of or reason ably extrapolate?

I'm approaching the game from entertainment first not physics lesson first. As part of that I like giving a 'hard space' feel but not go to your hardcore level.

But what we're trying to do here, I believe, is finding a way to make physics entertaining, no?

As such I want to impart all the lethality implied in high velocity impacts in space (I have quite a corpus of posting on this aspect), but give the option of being able to zoom off somewhere without crippling constraints.
[...]

But to "zoom off somewhere" without breaking real-worlds physics is sort of what the jump drive is supposed to do.

The funny part is that Traveller introduce not just one tech, but two - the latter of which, the M-Drive, is only necessary because the former, the jump drive, was given properties that require the latter.

Of course, if the physics implied by E=1/2m*v² stand in the way of your fun, by all means disregard them! But if what you actually wanted was possible by sticking to more physics, not less... I figure one would want to be aware of that.

 

[kilemall]

As stated, feel not limitations, entertainment and game effect over hardcore physics- as understood in our TL8 monkey planet.