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Old 06-17-2009, 02:42 AM   #11
Pomphis
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

Depends. The Bergenholm makes the entire ship inertialess, with consequences for boarding actions: people inside the ship are inertialess too. Ships must usually be hold tractorbeams in combat to damage them, as most beams simply push them away. But Lensmen doesn┤t care much about physics, so using it to design a campaign is much like using Tales of the Solar Patrol. Lensmen certainly is not bothered by relativity or stuff like that. Whether original momentum is retained is - IIRC - never discussed. And it is on a much larger scale: planetary bergenholms exist, and are countered by smashing the inertialess planet between two planets hitting it from opposite directions.
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Old 06-17-2009, 02:53 AM   #12
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Pomphis View Post
Depends. The Bergenholm makes the entire ship inertialess, with consequences for boarding actions: people inside the ship are inertialess too. Ships must usually be hold tractorbeams in combat to damage them, as most beams simply push them away. But Lensmen doesn┤t care much about physics, so using it to design a campaign is much like using Tales of the Solar Patrol. Lensmen certainly is not bothered by relativity or stuff like that. Whether original momentum is retained is - IIRC - never discussed. And it is on a much larger scale: planetary bergenholms exist, and are countered by smashing the inertialess planet between two planets hitting it from opposite directions.
Original momentum is indeed maintained; it comes back when the Bergenholm is switched off. In one book a rescue party had to match velocity in real space in order to retrieve the craft.
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Old 06-17-2009, 08:14 AM   #13
Fred Brackin
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Depends. The Bergenholm makes the entire ship inertialess, with consequences for boarding actions: people inside the ship are inertialess too.
The point about what is called "intrinsic velocity" made earlier is correct. It absolutely does "come back" when the Berg is switched off (even if this demands a preferred frame of reference).

Internal inertialessness is only the norm in early versions (specifically the Rodebush-Cleveland device rather than the Bergenholm itself). Artificial inertia is rapidly developed.

Patrolmen still train to deal with inertialess rnvironments in the era of Galactic Patrol and later books but it is seldom seen. SOP is to disable the Berg before you board.
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Old 06-17-2009, 10:26 AM   #14
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Hoverbombs would be the ultimate weapon
Spaceships doesn't go into a lot of detail, but I recall one sentence that says velocity acquired while under PV drive simply vanishes when you turn the PV off. So no hoverbombs with this definition of PV. Of course, this aggravates the matching course with Mars problem, as you can't gradually accumulate the proper vector while on your way. For interstellar travel it doesn't bear thinking about.

If you bounce radar off a ship under PV drive, what does the Doppler shift look like? I'd assume that you get Doppler readings for the true velocity. The radar equipment would have to determine your PV by taking the difference in position over different samples in time. The display probably returns both values as a matter of course.

Time dilation? It seems like half the point of PV would be to dodge such questions, so base it on true velocity. But Mach's Principle bugs me in that regard.
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Old 06-17-2009, 10:38 AM   #15
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Anaraxes View Post
Spaceships doesn't go into a lot of detail, but I recall one sentence that says velocity acquired while under PV drive simply vanishes when you turn the PV off. So no hoverbombs with this definition of PV. Of course, this aggravates the matching course with Mars problem, as you can't gradually accumulate the proper vector while on your way. For interstellar travel it doesn't bear thinking about.
The velocity is matched with Mars upon turning of the drive in Mars' orbit automagically?

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Originally Posted by Anaraxes View Post
If you bounce radar off a ship under PV drive, what does the Doppler shift look like? I'd assume that you get Doppler readings for the true velocity. The radar equipment would have to determine your PV by taking the difference in position over different samples in time. The display probably returns both values as a matter of course.
As if the ship has a true velocity matched with the RADAR-using craft? ;)
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Old 06-17-2009, 10:43 AM   #16
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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I recall one sentence that says velocity acquired while under PV drive simply vanishes when you turn the PV off. So no hoverbombs with this definition of PV.
The bombs do not acquire velocity while under PV. You use PV to go up to 1,000 miles. You switch off PV. You are accelerated downwards by gravity and gain real velocity. 900 miles down you switch PV on and go up to 1,000 miles again. Repeat.

Another option is to say that momentum is not maintained and that when PV is switched off the ship will be at rest relative to - for example - the mass having the greatest gravitional effect on this point of space.
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Old 06-17-2009, 11:00 AM   #17
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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The velocity is matched with Mars upon turning of the drive in Mars' orbit automagically?
I'd be tempted to go one further and put you in a stable orbit around Mars when you shut off the pseudovelocity.
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Old 06-17-2009, 11:03 AM   #18
David Johnston2
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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The bombs do not acquire velocity while under PV. You use PV to go up to 1,000 miles. You switch off PV. You are accelerated downwards by gravity and gain real velocity. 900 miles down you switch PV on and go up to 1,000 miles again. Repeat.
The result of course will be a bomb that vaporises in short order.
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Old 06-17-2009, 11:28 AM   #19
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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The result of course will be a bomb that vaporises in short order.
True, but if you multiply those distances by 20 it works just fine...
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Old 06-17-2009, 01:48 PM   #20
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

The problem with PV drives that just sort everything out for you (automagically! :-D What RoF do you get on that?) - is that it can unravel on you if you aren't careful.

If your drive leaves you at rest relative to the nearest large mass, that might be cool for giving ships the power to land and takeoff without rockets - but what happens if you want to rendezvous with an orbiting space station? You'll still need delta v good enough to match orbits with it. Or you could argue that nobody orbits anymore ("that's just so Newtonian") - and stations hover on their own PV drives - artificially maintaining a stationary orbit. Trouble is, the system is entirely non fail-safe. If a station's drives fail, it drops. Sooner or later there'll be an accident.

If the drive doesn't let you land on the other hand, but does deposit you neatly into a stable orbit for the altitude you are at when you switch off... which orbit is that then? Perfectly circular for that altitude perhaps? Okay - but at what inclination? Are you going east or west?

At the end of the day I have a nasty feeling that these thought experiments just prove the essential non-physicality of PV. Sigh. That's another way we won't be going to the stars to be added to the list.
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