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Old 02-26-2020, 05:12 PM   #81
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: Coolant [Spaceships]

Quote:
Originally Posted by Agemegos View Post
People sometimes assure me that Tsiolkovsky's equation applies to a hovering helicopter. Not if Δv = v(final) - v(initial) it doesn't.
Δv in that equation is your change in velocity due to your engine. If it happens to be equal magnitude but opposite direction to Δv caused by external forces, you hover.

It also doesn't apply to a hovering helicopter anyway, because the fuel/power requirements for hovering are not linear in weight, they're roughly order 3/2 in weight.
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Old 02-27-2020, 12:08 AM   #82
Johnny1A.2
 
Join Date: Feb 2007
Default Re: Coolant [Spaceships]

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Originally Posted by Fred Brackin View Post
The number of strategic warheads I have was 30,000. The great majority of the US contribution was 1/3rd megaton warheads on Minutemen. The W84 I believe. The only US warheads larger than that would have been soem on the rather small Atlas and Titan fleets and on SAC bombers. This number was never very high compared to the Minutemen even before they went MIRV.

So I think your number is a considerable overestimate even allowingf for larger Soviet warheads.
My recollection (which I have not double-checked, so you may well be right) was that each side had somewhere in the neighborhood of 30,000 warheads at their respective maximums. I was mentally shorthanding them at 1 megaton per bomb, which as you note is actually on the high end, most bombs run smaller.

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The rating for any c fractional vehicle is easy to calculate. It's the square root of the velocity in %c x the mass in antimatter equivalent. At c it would be 100% antimatter equivalent and you've spent the equivalent of the vehicle's mass in a 100% conversion drive to get there. C is where the Einstein equation (e=mc2) and the KE equation (ke=mv2) intersect.

So 12%c gives you 3.46 x the mass in antimatter with every metric ton of antimatter equivalent equalling 43 gigatons of TNT.

A quick google on "Daedalus probe" gives a scientific payload of 500 tons so that's 1.73 teratons rather than gigatons.
That's why I said 'at least' hundreds of gigatons. I was too tired to look up the figures on the second stage of Daedalus.

But imagine if Daedalus struck a habitable world in its target system. When you get up into teratons, you're starting to have major global effects. You'd probably want to design the second stage with enough delta-V left during the flyby to avoid an impact, just to be safe. Odds are enormously against it, but unlikely stuff does happen.
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Old 02-27-2020, 05:26 AM   #83
AlexanderHowl
 
Join Date: Feb 2016
Default Re: Coolant [Spaceships]

A reasonable protection against a high velocity attack would be to have stripped down large spacecraft to act as interceptors. A SM+8 spacecraft could have a control room, a fission reactor, a fuel tank for coolant, a reactionless engine, and sixteen ice armor. It would be capable of intercepting high velocity targets through getting in the way of their ballistic paths, either destroying them through impacts or forcing them to redirect and miss their target. The advantage of the ice armor is that it vaporizes during an impact and, while vaporizing, efficiently transfers heat to the solid parts of both spacecraft, greatly reducing any resulting high velocity debris by vaporizing the vast majority of the solid parts.

You could even have a SM+10 towing truck that positions SM+10 pieces of ice in the path of high velocity ballistic attacks (a SM+10 spaceship with eighteen ice armor and two core cargo holds full of ice). It would have a control room, a habitat, a hanger bay, two fusion reactors, three armor, three external clamps, four fuel tanks for coolant, and four reactionless engines. It could tow three SM+10 pieces of ice into position. Even an SM+14 spacecraft would be utterly destroyed if it hit a SM+10 piece of ice at 0.01c (something like 5 million dice of d-damage).
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Old 02-28-2020, 02:58 AM   #84
Aldric
 
Join Date: Nov 2015
Default Re: Coolant [Spaceships]

So, I don't think Coolant is the solution to the problem. It might be an interesting mechanic to add to combat, since it would most likely limit the use of weapons, but since a single round of attacks can easily destroy a ship, it doesn't seem very relevant. If only combat lasted longer...

As for limiting the speed and range of reactionless engines, just go with reaction engines, and spare yourself the trouble of explaining the reactionless ones.

As for the issue with ships that can reach high speeds, I think I'll add to my list of issues for my campaign.
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Old 02-28-2020, 05:49 AM   #85
AlexanderHowl
 
Join Date: Feb 2016
Default Re: Coolant [Spaceships]

Reactionless engines are easy to explain, especially if they are inertialless. The drive moves the frame of the spaceship but, while doing so, interferes with the radiation of heat from the frame of the spacecraft to other frames, thus requiring the venting of coolant to carry off waste heat. The drive utilizes an artificial negative mass effect to move the frame without inertia.

The FTL drive is an upgrade to the reactionless drive that removes the frame from four dimensional space-time but, since it is removed from four dimensional space-time, it cannot radiate heat, requiring the venting of coolant to carry off waste heat. Since the spaceship does not exist in four dimensional space-time, it cannot communicate or sense the outside Universe. The drive uses an artificial negative mass effect to remove the frame from normal four dimensional space-time, which causes its position relative the the outside Universe to change in a predictable as time passes (the vector does not change, but the velocity effectively increases to 3 parses per week number of drives).
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Old 02-28-2020, 10:29 AM   #86
Anthony
 
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Default Re: Coolant [Spaceships]

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Originally Posted by AlexanderHowl View Post
Reactionless engines are easy to explain, especially if they are inertialless. The drive moves the frame of the spaceship but, while doing so, interferes with the radiation of heat from the frame of the spacecraft to other frames, thus requiring the venting of coolant to carry off waste heat. The drive utilizes an artificial negative mass effect to move the frame without inertia.
That's a sublight warp drive, at which point you no longer need to care about kinetic impactors, with or without coolant.
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Old 02-28-2020, 01:12 PM   #87
AlexanderHowl
 
Join Date: Feb 2016
Default Re: Coolant [Spaceships]

Not necessarily, as you presumably cannot launch material objects from such a frame drive while you can from a sublight drive (the science gets wickedly complex when you talking about overlapping and intersecting frames). The frame drive would need to be turned off to deploy missiles and secondary spacecraft (which may have their own frame drives). Of course, the coolant release then becomes a signature (it still serves the purpose of forcing people to remass, allowing for more adventures).

Military tactics change with the introduction of such frame drives. First, you need coolant depots, which need to be defended and resupplied, similar to coaling stations a century ago. Second, warships would prefer beam weapons over missiles due to the issues of intersecting and overlapping frame drive fields. Third, missiles would be the preferred weapon of stations, since they would not have to worry about overlapping frame drive fields.
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Old 02-28-2020, 01:21 PM   #88
Ulzgoroth
 
Join Date: Jul 2008
Default Re: Coolant [Spaceships]

If the hot coolant is trapped in a drive bubble with the ship, it's not really being properly discarded until you drop the bubble and let it out, and will return heat to the vessel over time.
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Old 02-28-2020, 02:03 PM   #89
Anthony
 
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Default Re: Coolant [Spaceships]

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Originally Posted by AlexanderHowl View Post
Not necessarily, as you presumably cannot launch material objects from such a frame drive while you can from a sublight drive
It's perfectly possible to tune warp drive mechanics so an object with its own warp drive can exit. In any case, if it's necessary to shut the drive off, that will have a side effect of causing your velocity to revert to whatever it was before you turned the drive on.
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Old 02-29-2020, 11:42 PM   #90
Johnny1A.2
 
Join Date: Feb 2007
Default Re: Coolant [Spaceships]

Quote:
Originally Posted by Aldric View Post
So, I don't think Coolant is the solution to the problem. It might be an interesting mechanic to add to combat, since it would most likely limit the use of weapons, but since a single round of attacks can easily destroy a ship, it doesn't seem very relevant. If only combat lasted longer...

As for limiting the speed and range of reactionless engines, just go with reaction engines, and spare yourself the trouble of explaining the reactionless ones.
The problem with reaction drives is that they are inconveniently limited in delta-V and thrust. That's why so many SF writers use some sort of superscience drive. For a lot of SFnal settings, reaction drives aren't good enough (or rather, making them good enough has knock-on effects that wreck the setting assumptions).

An unmodified reactionless drive (that is, the classic by-your-bootstraps) has the opposite problem, it's too good (aside from violating conservation of momentum). Before long, some bright PC will get a funny look on his face and the next think you know people are throwing R-bombs at each other, and converting planets into asteroid belts.

So writers and GMs look for hybrid solutions.
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