Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 12-05-2017, 09:51 PM   #1
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default [Spaceships] Mass-driver realism

In Spaceships, the dominant selling point of the mass driver engine is that you can use anything as fuel. This is especially attractive for mining craft (as seen in designs in both SS6 and SS8). But I know that when it comes to the mass driver's weapon counterpart, the railgun, a major concern is the rails wear out very fast. This is potentially a bigger issue for the engine than the weapon; "able to use anything for ammo" isn't a selling point of the railgun, so if you need also need replacement parts its tolerable, but if you need to carry lots of replacement parts for your mass driver engine it sort of defeats the purpose.

So: is the promise of fee fuel for the mass driver realistic? Presumably they're not maintenance free, but will realistic mass drivers wear out much faster than other engines?
Michael Thayne is offline   Reply With Quote
Old 12-05-2017, 10:01 PM   #2
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Spaceships] Mass-driver realism

Mass driver rockets are presumably coilguns, not railguns. They don't have the same erosion problems (they have other issues, but those may not matter in a low thrust propulsion situation).
__________________
My GURPS site and Blog.
Anthony is online now   Reply With Quote
Old 12-05-2017, 10:09 PM   #3
Daigoro
 
Daigoro's Avatar
 
Join Date: Dec 2006
Location: Meifumado
Default Re: [Spaceships] Mass-driver realism

Quote:
Originally Posted by Michael Thayne View Post
I know that when it comes to the mass driver's weapon counterpart, the railgun, a major concern is the rails wear out very fast. This is potentially a bigger issue for the engine than the weapon;
I'da thought it be a bigger issue for the weapon as it needs to maintain a pinpoint accuracy that's unnecessary for the engine.
__________________
World Wikis:
Cyberpunk: Duopoly Nation
Fantasy: Dominion Cross
Space Opera: Behind the King's Eclipse
Steampunk: Colonial Steam
Daigoro is offline   Reply With Quote
Old 12-05-2017, 10:26 PM   #4
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Mass-driver realism

Quote:
Originally Posted by Anthony View Post
Mass driver rockets are presumably coilguns, not railguns. They don't have the same erosion problems (they have other issues, but those may not matter in a low thrust propulsion situation).
What are those other issues?
Michael Thayne is offline   Reply With Quote
Old 12-06-2017, 12:43 AM   #5
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Spaceships] Mass-driver realism

Quote:
Originally Posted by Michael Thayne View Post
What are those other issues?
Typically relatively low acceleration, and it's hard to aim and stabilize the projectile in the barrel. Both can be mitigated by producing a big, low density system, which won't work very well as a weapon but is perfectly okay for slowly pushing an asteroid around.
__________________
My GURPS site and Blog.
Anthony is online now   Reply With Quote
Old 12-06-2017, 12:34 PM   #6
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Mass-driver realism

Is that likely to be a barrier to getting the kind of performance assumed in Spaceships? Or is the lack of accuracy fine for a propulsion system?
Michael Thayne is offline   Reply With Quote
Old 12-06-2017, 04:58 PM   #7
AlexanderHowl
 
Join Date: Feb 2016
Default Re: [Spaceships] Mass-driver realism

Accuracy does not matter for thrust. The real problem with mass drivers are that they are energy hogs because of the inefficiency of ionizing random matter. While people can talk about ISRU with mass drivers, water is more common than dirt in the outer solar system, and a fusion drive that uses water as reaction mass is vastly superior to a mass driver (meaning that mass drivers are only really useful in the Inner Solar System).
AlexanderHowl is offline   Reply With Quote
Old 12-06-2017, 09:41 PM   #8
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Mass-driver realism

Quote:
Originally Posted by AlexanderHowl View Post
Accuracy does not matter for thrust. The real problem with mass drivers are that they are energy hogs because of the inefficiency of ionizing random matter. While people can talk about ISRU with mass drivers, water is more common than dirt in the outer solar system, and a fusion drive that uses water as reaction mass is vastly superior to a mass driver (meaning that mass drivers are only really useful in the Inner Solar System).
I don't think the usual mass driver propulsion plan is to ionize random dirt. I think the plan is to have reusable metal buckets on tethers.

As for mass-drivers vs. drives that use water reaction mass, obviously volatile miners will want to use volatiles as reaction mass. If they really can be made to work as assumed in Spaceships, though, they'd shine for purposes of mining stony and metallic asteroids.
Michael Thayne is offline   Reply With Quote
Old 12-06-2017, 09:51 PM   #9
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: [Spaceships] Mass-driver realism

Looking at this more, I'm kind of wondering why mass drivers weren't listed in Spaceships as TL8—sure mass driver propulsion hasn't been developed yet, but neither have Orion drives or nuclear thermal rockets, both TL7.
Michael Thayne is offline   Reply With Quote
Old 12-06-2017, 10:02 PM   #10
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Spaceships] Mass-driver realism

They both come under the category of "buildable at TL 7, but a really stupid idea".
__________________
My GURPS site and Blog.
Anthony is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 12:50 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.