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 > Traveller

Reply
 
Thread Tools Display Modes
Old 05-31-2021, 03:18 PM   #11
Toltrin
 
Toltrin's Avatar
 
Join Date: Mar 2008
Location: Oregon
Default Re: Jump Distance

Thank you!
So, extra fuel tank in the cargo hold, external fuel tanks (that probably lower aerodynamics) and fuel processors that must weigh a ton.
Are there any alternate or advanced drive systems one could install in a 100t scout class that could jump 4 or even 5 with special fuel other than deuterium?
We have a espionage campaign you see...
__________________
My OGRE/GEV blog , CP Alpha's new home
My email
Toltrin is offline   Reply With Quote
Old 05-31-2021, 05:20 PM   #12
ericbsmith
 
ericbsmith's Avatar
 
Join Date: Aug 2004
Location: Binghamton, NY, USA. Near the river Styx in the 5th Circle.
Default Re: Jump Distance

Quote:
Originally Posted by Toltrin View Post
Thank you!
So, extra fuel tank in the cargo hold, external fuel tanks (that probably lower aerodynamics) and fuel processors that must weigh a ton.
All ships get a minimal fuel processor built into their fuel tanks. You can install a much larger one as a ship system which will allow ships to refuel much faster. In practice the only ships that usually have the larger fuel processor are deep scouts which routinely travel through uninhabited systems or fuel tenders which scoop gas giants to process the raw hydrogen then sell the refined fuel to ships passing through the system.

Quote:
Originally Posted by Toltrin View Post
Are there any alternate or advanced drive systems one could install in a 100t scout class that could jump 4 or even 5 with special fuel other than deuterium?
We have a espionage campaign you see...
Not by the rules. If you want to design a ship that can go Jump-4 or Jump-5 you need to install a J-4 or J-5 stardrive* and supply it with fuel tanks that take up 40% or 50% of it's volume. By the RAW of the setting there is no alternate fuel source that allows you to jump for less fuel than the 10% of ship volume per parsec (though the creation of such a drive might be a good plot point in an adventure, and would be highly sought after by EVERYBODY, who would be tripping over each other trying get their hands on such an innovation).

Theoretically a ship could have, say, 20% of it's volume in internal tanks and 20% in external drop tanks, giving it the capability to jump 2 parsecs on internal fuel or 4 parsecs if it has drop tanks. But that's a design decision that would need to be made when the ship is created; most ships just rely on internal fuel tanks and have just enough internal fuel to make one jump of whatever their maximum distance is.

* Note that a Scout has only a J-2 stardrive installed, so even if you somehow fed it more fuel it can't jump more than 2 parsecs without replacing the stardrive with a much more expensive one.
__________________
Eric B. Smith GURPS Data File Coordinator
GURPSLand
The future keeps telling us what the past was about. You make the past mean different things by what you do with the time that comes after.

Last edited by ericbsmith; 05-31-2021 at 05:28 PM.
ericbsmith is online now   Reply With Quote
Old 05-31-2021, 05:31 PM   #13
thrash
 
thrash's Avatar
 
Join Date: Aug 2004
Location: traveller
Default Re: Jump Distance

Quote:
Originally Posted by Toltrin View Post
Are there any alternate or advanced drive systems one could install in a 100t scout class that could jump 4 or even 5 with special fuel other than deuterium?
Eric has covered the special fuel angle. Note that standard liquid hydrogen jump "fuel" is protium, not deuterium.

There is a canonical 100-dton ship that attains jump-4: the express boat (xboat). It achieves this by sacrificing maneuver drives (and, in some versions of Traveller, a power plant).

Depending on the version, you could trade three staterooms, fire control, and three dtons of cargo for 20 dtons of fuel tank and manage two jump-2's with a modified Type S scout/courier. That would allow you to jump into a system 2 hexes away and jump back again without refueling, or cross a 4 hex gap in two jumps.
thrash is offline   Reply With Quote
Old 05-31-2021, 11:30 PM   #14
Pomphis
 
Join Date: Oct 2004
Default Re: Jump Distance

There is another trick: build a J-1 or J-2 or J-3 ship. Put in additional tanks. Fill the additional tanks not with liquid hydrogen, but with stuff with a significantly higher hydrogen density. Jump. Then process the stuff from the additional tanks in your onboard fuel processor, put the resulting hydrogen into the jump tank to refuel it and expel the waste.

Methane is CH4, that is each molecule has 4 hydrogen atoms. IIRC density is comparable to liquid hydrogen. So you can process 1 dt methane into 4 dt hydrogen. We discussed this very long ago on the old Pyramid boards, I am not sure whether I remember the density for methane correctly, better check that. IIRC there were also other substances that could be used to store hydrogen in much higher density than liquid hydrogen has.

Note that higher density means more mass, so such ships will have noticably less acceleration as long as the reserve fuel is carried.
Pomphis is offline   Reply With Quote
Old 06-02-2021, 12:56 PM   #15
Toltrin
 
Toltrin's Avatar
 
Join Date: Mar 2008
Location: Oregon
Default Re: Jump Distance

Quote:
Originally Posted by Pomphis View Post
There is another trick: build a J-1 or J-2 or J-3 ship. Put in additional tanks. Fill the additional tanks not with liquid hydrogen, but with stuff with a significantly higher hydrogen density. Jump. Then process the stuff from the additional tanks in your onboard fuel processor, put the resulting hydrogen into the jump tank to refuel it and expel the waste.

Methane is CH4, that is each molecule has 4 hydrogen atoms. IIRC density is comparable to liquid hydrogen. So you can process 1 dt methane into 4 dt hydrogen. We discussed this very long ago on the old Pyramid boards, I am not sure whether I remember the density for methane correctly, better check that. IIRC there were also other substances that could be used to store hydrogen in much higher density than liquid hydrogen has.

Note that higher density means more mass, so such ships will have noticably less acceleration as long as the reserve fuel is carried.
We are going to use this for how this 120 ton scout manages to escape on a jump-4 distance from Imperial authorities into the "badlands". Thank you!
__________________
My OGRE/GEV blog , CP Alpha's new home
My email
Toltrin is offline   Reply With Quote
Old 06-02-2021, 08:04 PM   #16
malloyd
 
Join Date: Jun 2006
Default Re: Jump Distance

Quote:
Originally Posted by Pomphis View Post
IIRC there were also other substances that could be used to store hydrogen is much higher density than liquid hydrogen has .
This is not really true - in an ordinary liquid or solid most of the volume is occupied by atoms, and atoms of an element generally have the same volume regardless of the environment. Since adding anything else in with the hydrogen to form other molecules introduces atoms of other stuff, that will themselves need some volume, this will almost always results in *fewer* actual hydrogen atoms per cubic meter. There's a bit of leeway, but no compound is going to double the amount of hydrogen per liter, let alone do better. I believe the best one is hydrazine (N2H4), which gets you 1.79 times as much hydrogen per liter as cryogenic liquid hydrogen. Of course it's quite toxic and spontaneously explosive.....

The real kicker is metallic hydrogen, which, giving that stuff actually labeled "superdense" is available in stable enough form to use as armor, should be *easy* with Traveller tech. And totally destructive to canon ship designs, with theoretical densities *starting* at over 10 times that of liquid hydrogen and going up to like 60 times for some phases.
__________________
--
MA Lloyd
malloyd is offline   Reply With Quote
Old 06-02-2021, 08:49 PM   #17
Fred Brackin
 
Join Date: Aug 2007
Default Re: Jump Distance

Quote:
Originally Posted by malloyd View Post
T
The real kicker is metallic hydrogen, which, giving that stuff actually labeled "superdense" is available in stable enough form to use as armor, should be *easy* with Traveller tech. And totally destructive to canon ship designs, with theoretical densities *starting* at over 10 times that of liquid hydrogen and going up to like 60 times for some phases.
Yes, especially since Traveller LH2 tanks almost have to invovle superscience to keep that hydrogen without it leaking away. NASA simp;ly always ordered twice as much LH2 as it needed knowing half of it would just seep out of the tanks before it could be used.

My personal speculation is that the fuel tanks are lined with repulsor projectors so the hydrogen never touches the walls of the tanks. compressing the hydrogen to the metallic phase would take lots of energy but fusion power is cheap.

Of course as you hint using metallic hydrogen tankage means everyone maxes out their J-drive to the limits of their TL (J-6 for the 3rd Imperium). They might even carry fuel for 2 J-6s.
__________________
Fred Brackin
Fred Brackin is offline   Reply With Quote
Old 06-02-2021, 09:05 PM   #18
thrash
 
thrash's Avatar
 
Join Date: Aug 2004
Location: traveller
Default Re: Jump Distance

Quote:
Originally Posted by Fred Brackin View Post
Of course as you hint using metallic hydrogen tankage means everyone maxes out their J-drive to the limits of their TL (J-6 for the 3rd Imperium). They might even carry fuel for 2 J-6s.
Makes those "Fuel" hits or "Fuel Tanks Shattered" results much more exciting, though.
thrash is offline   Reply With Quote
Old 06-04-2021, 07:17 AM   #19
malloyd
 
Join Date: Jun 2006
Default Re: Jump Distance

Quote:
Originally Posted by thrash View Post
Makes those "Fuel" hits or "Fuel Tanks Shattered" results much more exciting, though.
For some applications that's a plus - it gives you back the "damaged ship explodes" result that's otherwise quite hard to justify in a space battle, but all over space war fiction - presumably by flawed analogy to wet navy ships that can explode if you can get a hit into the magazine.
__________________
--
MA Lloyd
malloyd is offline   Reply With Quote
Old 06-04-2021, 08:29 PM   #20
Toltrin
 
Toltrin's Avatar
 
Join Date: Mar 2008
Location: Oregon
Default Re: Jump Distance

Hydrozone, CH4, metallic hydrogen - so many choices but I am betting all are on different tech levels.
Are there not civilizations that have metallic hydrogen and double J-6 drives even before the 3rd Emperium?
__________________
My OGRE/GEV blog , CP Alpha's new home
My email
Toltrin is offline   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 01:06 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2021, vBulletin Solutions, Inc.