100 dT Huntress model

[Anonymous]

Just a quickie on temperatures, objects in orbit around earth experience temperatures up to 200 deg C when sitting in the light of the sun, if your vehicle is orbiting as ours do now it will plummet to something like -160 deg C as you move to the dark side.

If we're talking about ships designed to skim fuel from a gas giant it's all hand waving but the temperature gets pretty hot at the core so it could be quite toasty somewhere further up the atmosphere but who knows how deep you need to go to skim fuel?

Planets close in to their stars can get stupid hot too, if you were orbiting mercury the temperature in the sunlight things would be somewhat north of tropical!

The kind of temperatures therefore that ships would endure at the relatively slow speeds their aerodynamic (or lack of) shape can handle, I don't think we need to worry about.

:mrgreen:

 

[Anonymous]

And, if I ruled the world and decided on how traffic control worked (OK, it maybe a bad idea to put me in charge of stuff like that) I'm pretty sure a ship would match the speed of the orbiting planet on it's approach vector from the 100D jump zones so that as it was ready to descend thru the atmosphere, it was stationary relative to the planet below.

Would you really want all those several thousand tonne ships hurtling around your atmosphere waiting for an accident to happen? They'd be descending over no/low population areas before moving to land at a sedate speed.

Tho more likely doing business up at the high port with very few inter stellar ships ever landing on surface. But OK, you don't get to make the ships look cool if they don't need to be streamlined or remotely aerodynamic.

Back to your regularly scheduled topic now

 

[phavoc]

According to the scan info I could find on Traveller gas giant refuelling, it's all done at the higher altitudes with lower pressure. Even a Trav ship going too deep would find itself crushed unless it was designed to operate in that specific environment (much like a research submersible can go so much deeper than a regular submarine).

And the actual techniques (speed, etc) are woefully understood or explained in the game. Don't quote me on where I got this (as I don't recall), but this is what I could find:

At about 38,000km height the atmosphere around a typical gas giant is essentially a vacuum. Ships refuel at an altitude of 36,000 to 36,500 km. The atmospheric pressure is around 1 (earth normal). Drop down to 35,000km and the pressure is 300. The lower you go the denser and hotter it gets, so the more thrust you need to actually "fly" in it. With a gravitic drive you can easily go up and down, but that doesn't help with your scooping process. You can't just sit there with your baffles open and say to the hydrogen 'Get in mah fuel tanks!'. Or belly, whichever you prefer.

 

[Condottiere]

Submarines in this case being SDBs lying doggo waiting for an unauthorized skimming attempt.

 

[Bardicheart]

According to the scan info I could find on Traveller gas giant refuelling, it's all done at the higher altitudes with lower pressure. Even a Trav ship going too deep would find itself crushed unless it was designed to operate in that specific environment (much like a research submersible can go so much deeper than a regular submarine).

Pretty much my understanding of it. Plus hydrogen being a light gas would tend to drift higher in the atmosphere. Although its theorized that beneath Jupiter's crushing atmosphere is a 25,000 mile deep ocean of liquid metallic hydrogen. Would make refueling a snap, now all we need is a REALLY long hose. :lol:

Now how to fit a 300 mile long hose in the ship's locker... hmmm... 8) Why is the GM glaring at me... again?

 

[phavoc]

Submarines in this case being SDBs lying doggo waiting for an unauthorized skimming attempt.

From everything I've read the only unauthorized refueling that might occur would be if a Zho fleet showed up in Imperial space to top off their tanks with a note of "Just passing through! Don't mind us."

Gas giants aren't claimed territory as far as I understand. A planets legal influence is only out to 100D. Outside that is Imperial territory. And a gas giant is b-i-g.

I really wish there was more background info on exactly why and how a ship is so much more vulnerable while refueling. On the one hand it's more or less a sitting duck at a few hundred KPH, but the way the make it out to be is that it's a sitting duck WITH a bullseye painted on the hull and eggshells for hull plating.

 

[Anonymous]

That's what I never got about refueling from gas giants as standard proc for warships. (It's mentioned often enough as to seem standard proc, whether it is or not I don't really know)

The vulnerability and then the time to skim and process fuel makes it contrary to what I imagine are good practices in time of war.

I can see maintaining some kind of fuel station in orbit of the GG so the fuel was skimmed, processed and ready to roll but I'd see that happening at the star port too.

It's not like you can have a prearranged fuel point in the middle of nowhere as you still take a week to jump there and you then waste the fuel jumping out.

Even from a commercial point of view, the time it takes for a 1 or 2G ship to refuel and then transit in system to the main world isn't worth the saving on unrefined fuel you process while your ship is docked and you're trading/going about your business. It maybe in some systems where the GG is closer to the main world but as we don't have much system information for distances it just gets hand waved.

 

[Bardicheart]

That's what I never got about refueling from gas giants as standard proc for warships. (It's mentioned often enough as to seem standard proc, whether it is or not I don't really know)

The vulnerability and then the time to skim and process fuel makes it contrary to what I imagine are good practices in time of war.

I've had the same question, and the following is the only way I ever made sense of it.

Jump travel doesn't seem to be precise. You don't spend exactly one week in jump space. Sometimes its 6 days, sometimes its 8, the range seems to be 6.4 to 7.6 days. That's a problem if you're jumping a fleet into a system. What happens if part of your fleet arrives on day 6, the bulk on day 7, and the remainder on day 8? Worse, it might be your support ships that arrive on day 6 while your big guns don't arrive until day 8 some 30 hrs later.

That raised the question to me of how precise jump locations are, exactly how predictable is where you re-enter? Since you're cut off from all outside communication in what has been described as a kind of pocket universe, it would stand to reason sensors don't work which means navigation would all depend on those jump coords you punched in before the jump. I don't think you would have part of the fleet jumping in on the opposite side of a planetary system, but it seems reasonable to think there would be some dispersion; maybe 2d6 x 100,000 km or something.

So assuming the above is true, how to cope. I would jump a fleet into the outer regions of a planetary system. Far enough out it would take most system defense ships several days to intercept, giving the fleet time to arrive and organize. Since you're starting that far out, gas giants are probably something you'll pass on your way in. Once you've secured enough of the system to control one, refueling there (or any other source of hydrogen in the outer system) makes sense.

Meanwhile the fleet pushes inward and works at securing the outer worlds, locating and neutralizing outposts, picket forces, raiders (SDBs left behind to hit supply ships and harass the invader, the idea being to slow them up until hopefully help can arrive; assuming the invaded system has outside allies that can jump in to break the siege), etc. before moving on the main world, enveloping it and prepping for either orbital bombardment or ground invasion or both.

At least that's the general scenario I always imagined playing out, again YMMV.

An slightly back on topic, the above scenario is something I would love to eventually do an animation / short movie of. A fleet jumping in, defense forces intercepting, etc. Would be a ton of work but so very cool!

 

[Anonymous]

I think I raised the same question a while back and got an answer that somewhere in the annals of Traveller one version had a thing called something like a jump sync.

It's more hand waving to cover up the flaws that playing the game reveals but it's all good, every thing is a hand wave. See sig...

I must confess that with something as precise as I imagine the calculations to jump being, that there would be no more accurate a way of predicting where and when you drop out of jump is a bit silly to me.

Have the astrogator earn his pay (tho a computer would do it better) and allow the roll to greatly influence the accuracy both in time and space of the exit from jump.

With regard to the fleet thing, I'm not much into big space battles and don't think how their strategies might be played out. I think to develop the strategy tho you have to have an intricate knowledge of the tools. Defining the way ships jump in detail (making it up!) is the way forward!

There are lots of vagaries in Traveller, the details that make bringing a future setting to life are missing.

Now I am fine with adding the details in to my games, sometimes my players are too!

I'm often interested in what others do which is why I'm here but some people really get caught up in being right tho and it's just plain weird. It is a game isn't it?

 

[Anonymous]

Something related I posted recently too, when you enter jump you're supposed to be stationary.

Stationary compared to what?

The system you left? The planet you left? The system you're heading towards? The rotation of the spiral of the galaxy you're in or the movement of the galaxy itself?

None of which is really practical to answer in game terms so should it be ignored?

If you exit jump with no velocity (compared to something) and you're about to go toe to toe with your enemy, do you need velocity to be at the advantage when fighting? If so, best put the pedal to the metal post haste! If you've done that out in the blackness of space, will your grav thrusters (which aren't using reaction fuel) have a signature of some kind thats traveling out away from you faster than you're traveling which your enemies are gonna pick up before you get to engagement range. They're gonna see you coming.

All this kind of stuff I'd love to see defined.

Not cos I want their to be a right answer, there isn't a right answer.

Cos I want a constant answer with which to game with.

Anyway, I am way OT in your thread, apologies.

 

[Bardicheart]

Anyway, I am way OT in your thread, apologies.

Well seeing as I'm kinda the pirate who hijacked his own thread, no apologies necessary. Didn't get any work done on the ship model today. To be honest I've just been too tired and worn out to focus on it and I get really sloppy and unimaginative when I tried to work while tired. Maybe get back to it tomorrow.

 

[Anonymous]

Yeah, I've had that problem the last few days. I've been working out stuff for the game I'm GMing and haven't spent much time on the setting I'd like to see clear up all this weird sh!t... Ever get the feeling you bit off more than you can chew?

 

[dragoner]

Something related I posted recently too, when you enter jump you're supposed to be stationary.

Originally vector was maintained, did this change?

 

[Anonymous]

Heaven knows!

It's been written down in some versions of Traveller but I'm not sure it says anything in MgT.

Page 142 (or 141 of the PDF) makes no mention of the ships velocity prior to entering jump.

 

[dragoner]

Probably best not to dig too deep anyways, everything is moving, but I can see reasons for both.

 

[Bardicheart]

Yeah, I've had that problem the last few days. I've been working out stuff for the game I'm GMing and haven't spent much time on the setting I'd like to see clear up all this weird sh!t... Ever get the feeling you bit off more than you can chew?

Well, lets see... I originally started this project cause I thought it would be something fun and quick I could knock out in a couple of days while taking a break from a more realistic interplanetary ship concept I had been working on that was taking forever and also a complex temple "kit" project I'm doing for commercial release when its done. Now I'm talking about doing animations and short movies with it. So... yes, all the time! :lol:

 

[Anonymous]

Shortly Sir (when I've been to the beer shop), I'll raise a glass to you!

 

[phavoc]

That's what I never got about refueling from gas giants as standard proc for warships. (It's mentioned often enough as to seem standard proc, whether it is or not I don't really know)

The vulnerability and then the time to skim and process fuel makes it contrary to what I imagine are good practices in time of war.

I can see maintaining some kind of fuel station in orbit of the GG so the fuel was skimmed, processed and ready to roll but I'd see that happening at the star port too.

Aye, that's where the term High Guard was coined. While some ships refueled the others would hold a "high guard" position above them for protection from those dastardly lurking 400ton SDB's who are the scourge of system invaders everywhere.

Something related I posted recently too, when you enter jump you're supposed to be stationary.

Originally vector was maintained, did this change?

There was an article in JTAS #24 by Miller about jumpspace. Basically he states:
(1) The laws of conservation of momentum must be maintained, so civilian ships reduce their velocity to zero.
(2) Military ships don't, so they can have speed upon exit in the new system, directing their exit vector towards their destination. So they accelerate constantly in their departure system to they can decelerate in their arrival system.
(3) When the two systems have a high relative proper motion with each other this has to be factored into things when computing speeds and directions for when you arrive at the new system.

JTAS has covered a lot of things over the years. I am constantly rediscovering things by reading the back issues. You can purchase the entire set (up through the Challenge issues) from FFE for $20.

 

[Anonymous]

JTAS has covered a lot of things over the years. I am constantly rediscovering things by reading the back issues. You can purchase the entire set (up through the Challenge issues) from FFE for $20.

I'm kinda hoping that the Traveller Companion that's talked of for 2nd Ed MgT will bring the relevant stuff together in one place. It might be a bridge too far!

I get that it's all out there, it's just in so many places, spread over different versions of the rules.

I know, I want my cake and eat it

 

[Anonymous]

There was an article in JTAS #24 by Miller about jumpspace. Basically he states:
(1) The laws of conservation of momentum must be maintained, so civilian ships reduce their velocity to zero.
(2) Military ships don't, so they can have speed upon exit in the new system, directing their exit vector towards their destination. So they accelerate constantly in their departure system to they can decelerate in their arrival system.
(3) When the two systems have a high relative proper motion with each other this has to be factored into things when computing speeds and directions for when you arrive at the new system.

What's to stop a commercial ship calculating the correct vector to leave a system on to drop out of jump on course and at speed? Make it a damn sight harder for pirates to attack.

At the end of the day it's just math and astrogation/data. Just as we have charts of currents and depths for shipping these days I can see that information routinely in any ship's computer and updated automatically. Maybe as part of the berthing fees there's a data dump of the latest astrodata?