Long Voyages of Exploration

[TKalbfus]

To suck in enough material for an interstellar ramjet, the scoops have to be on the order of 100,000 kilometers in radius. Very large.

But the scoops aren't made of solid material. The scoops is a giant magnetic field that is 100,000 km in radius. The superconducting coils that generate that field aren't necessarily that big! Magnetic fields weigh nothing, they are just lines of force. You just need a superconductor that can carry a large amount of electric current through a loop. The lines of magnetic force are perpendicular to the direction of the electric current. The hydrogen is ionized by forward facing lasers. Since their is not much hydrogen in space, it doesn't take that much energy to ionize them, this energy is increased dur to doppler shifting of the ship's forward motion. The hydrogen has to be slowed down in relation to the ship and collected. Some of the hydrogen has to be fused to continue to push against the interstellar medium while the rest is collected and stored for use by the jump drive. This is not a standard use of an interstellar ramjet, it provides little net thrust and drag puts an upper limit on its velocity, but for the purposes of collecting hydrogen for a jump drive, an interstellar ram jet works fine.
It'll probably go no faster than 30% of the speed of light as the drag will then be greater that the thrust that can be produced by fusion.

 

[savage]

I suppose in a traveller campaign you could use about anything you wanted...but how much energy is
this system going to use to obtain the hydrogen for your jump...and plant. Are you certain you'd believe it to be a break even effort. Your lasers would have to specialized...probably use up more ep...etc...

just a thought...

 

[Rupert Boleyn]

Originally posted by marginaleye:

Actually, launching the expedition a little later -- perhaps during a particularly bleak part of the Long Night -- might make more sense. I suspect that the very early Solomani didn't know enough about jump drives to foresee the problems spending decades without overhauls would cause...

The Terrans were using jump-drive for intra-system jumps for a number of years before they made the trip to Barnard's Star, so I imagine that they'd have run across the effects of poorly maintained drives before they made TL10, let alone TL11 and Jump-2.

 

[TKalbfus]

I suppose in a traveller campaign you could use about anything you wanted...but how much energy is
this system going to use to obtain the hydrogen for your jump...and plant. Are you certain you'd believe it to be a break even effort. Your lasers would have to specialized...probably use up more ep...etc...

just a thought...

In a Traveller campaign, the actual velocity of the Starship doesn't matter that much. What really gets the starship places is the Jump Drive. I'm just repeating what I heard from various sources about the Interstellar Ramjet and applying it toward the Traveller fictional setting. There is normally not much use for a slower than light StarShip in the traveller setting, but the ramjet's ability to collect hydrogen enroute makes this particular starship interesting. I don't know the actual numbers. Originally the Ramjet was supposed to be able to accelerate at 1-G indefinitely with higher speeds sweeping up more hydrogen per second, but with increase in velocity, the relative kinetic energy of each hydrogen atom increases to the square of its relative velocity to the ramjet. Much depends on how efficient the fusion reactor is. I believe the energy released by fusion would initially be many times its kinetic energy, but each hydrogen atom needs to be slowed down and at higher velocities, this required increasingly more energy. I remember reading somewhere that the maximum velocity was somewhere less than half the speed of light. 1/3 C sounds reasonable. For game purposes assume it takes a few days to collect the hydrogen to make a jump. The jump could be something like Jump-6. One good source of deck plans would be the "Lighthouse" from the old Alternity game, it is basically a mobile starport.

Tom

 

[marginaleye]

I suppose in a traveller campaign you could use about anything you wanted...but how much energy is
this system going to use to obtain the hydrogen for your jump...and plant. Are you certain you'd believe it to be a break even effort. Your lasers would have to specialized...probably use up more ep...etc...

I wonder whether it would be possible to "scoop" interstellar hydrogen using some kind of gravitic, rather than magnetic, technology. The canonical limitations of gravitic technology are... unclear. On the one hand, "tractor beams" don't seem to exist, but "repulsors" definitely do exist as a point-defense weapon against missles. According to the T4 version of F. F. & S., gravitic technology somehow gets involved in the low-berth freezing process at a fairly low Tech Level (10? 11? I don't have a copy of the book with me), implying that other strange, hitherto-unmentioned spin-off applications are at least possible.

But the ability to use gravitics to scoop interstellar hydrogen would imply that "deflector shields" for knocking aside chunkier things (dust particles, micrometeorites, and so forth) could exist, too... and I don't think there's even a hint of those in the canonical literature, so perhaps this isn't such a good idea afterall.

Or perhaps they are possible, but since nobody travels at a significant fraction of the speed of light, there was never much of an incentive to develop the technology (since robust hulls are, under ordinary circumstances, good enough).

 

[savage]

I'd suggest a conservative path. gravitics vs magnetics. Well at least magnetics has founding below the galactic level of astrophysics. Anti-Gravity plates and repulsors have been one of the fantasy elements of Traveller. Magentics isn't...


Savage

 

[TKalbfus]

And gravity is a short range force when used on ships. A gravity field of 1-G on the ships plates would drop to 1/4-g if you removed to one ship's radius out. You need a scoop that's 200,000 km in diameter. To accomplish this with gravity, you need a pole or cable with an extremely strong gravitational field that pulls all matter toward it, it's not only going to pull hydrogen, but the ships crew as well. The gravity generator will also likely be destroyed if it pulls too much stuff toward itself. The magnetic field repells and channels the hydrogen through the starship without contact.

 

[Drakon]

Originally posted by Larsen E. Whipsnade:

Sir,

Don't call me Sir, I work for a living and both my parents were married :smile:

There's also trouble with the region of space surrounding Sol. It seems that we're in a bit of a 'bubble'; a bubble hundreds of light years wide, that contains less bits of interstellar material than the average. Even if you could project the Bussard's 'wings', our neighborhood has has precious little for it to scoop.

Are you sure? I thought the Gould belt had more interstellar material than average.

I like it. Like you, I too have spent time in shipyards as a 'visitor', 'yardbird', and 'tech rep'. I'd add a few extra bits to your baggie idea though; internal scaffolding for workers and equipment, external hard panels for micrometeorite protection and the occasional bumps from small craft, modular locks for personnel, tools, parts, etc., and lots and lots of pressure tight tool cribs, changing rooms, chow halls, medical bays, etc.

All great ideas. But what I was thinking is you have the drydock ship, with the "baggie" mounted to the side of the hull. All your changing rooms, tool cribs, etc. everything that is not required to be IN the dock, but required FOR the dock, in the ship. You unfurl the baggie, with the internal scaffolding, from the side of the ship.

And the "sausage" on the side of the hull, great!

 

[Whipsnade]

Drakon wrote:

"Don't call me Sir, I work for a living and both my parents were married :smile:"


Drakon,

Sorry, force of habit. I'm an old fuddy duddy among other things.

"Are you sure? I thought the Gould belt had more interstellar material than average."

Yes, quite sure. It's from the JTAS boards and was originally brought up by a very detail oriented fellow who happened to be working on an update of the Islands Subsectors. The question that had bedeviled him was why the ESA mission had traveled so far, as far as the Great Rift when so many other, closer candidates were available.

Of course, the real reason for the journey's length is a metagame one; it fit the idea behind TCS neatly. However, the fellow in question discovered information about this 'bubble'; something that had only been suspected and detected in the last decade or so, and used that new fact to 'explain' the length of the ESA's trip.

"All great ideas. But what I was thinking is you have the drydock ship, with the "baggie" mounted to the side of the hull."

Nifty! I was thinking of something more 'free-form'; you build your drydock to suit the size and shape of each ship. A drydock ship; with a fixed 'baggie' size, would most certainly work. After all, it's what we use now!

"And the "sausage" on the side of the hull, great!"

Think graving docks or repairs slips. Some jobs won't require a full dry dock, just a protected area or two on the hull will do. Slap a 'sausage' in place, remove the hull plating, and get the job done.


Sincerely,
Larsen

 

[Drakon]

Originally posted by Larsen E. Whipsnade:
Sorry, force of habit. I'm an old fuddy duddy among other things.

And my response is force of habit too. I was enlisted and so...

As for the bubble/Gould belt thingy, it looks like we are both right in this respect. The sun is in the middle of a "local bubble" where interstellar matter is 1/20th the level of what is found in the rest of the galaxy. However, this is part of the Gould belt complex, that the sun is traveling through at the moment.

Which makes sense once you think about it. The Gould belt is a star forming region, which means it is likely to make short lived, massive stars. Stars going nova will blow bubbles in the interstellar gas.

Nifty! I was thinking of something more 'free-form'; you build your drydock to suit the size and shape of each ship. A drydock ship; with a fixed 'baggie' size, would most certainly work. After all, it's what we use now!

Is there any reason why the same ship cannot build either? Either a free standing baggie, or one attached to the hull of a set size? Other than storage space considerations.

 

[marginaleye]

Nifty! I was thinking of something more 'free-form'; you build your drydock to suit the size and shape of each ship. A drydock ship; with a fixed 'baggie' size, would most certainly work. After all, it's what we use now!

</font><blockquote>quote:</font><hr />
Is there any reason why the same ship cannot build either? Either a free standing baggie, or one attached to the hull of a set size? Other than storage space considerations.

</font>[/QUOTE]In a previous message, I stole an idea from Arthur C. Clarke, and suggested protecting the bow of the starship from dust- and micrometeorite-erosion with an ablative shield of ice (although, I suppose, a big circular slab of non-ablative crystaliron, or even superdense, would probably work just as well). Suppose the hull of the ship is basically cylindrical, and the "shield" is circular. Suppose, furthermore, that the diameter of the shield is greater than that of the hull (so the ship looks a bit like mushroom, with a long thick stem, and a small cap).

It's easy to imagine the "collapsible dry-dock components" being stored (packed flat) on the trailing edge of the shield. If extensive repairs or maintenance had to be conducted, one or more of these components could be unpacked, stretched aft, and inflated, covering the parts of the hull in need of attention. You could even build tracks and attachment points right onto the hull to facilitate this.

Does this sound like a sensible idea?

 

[savage]

Gee! I think that's where I was going with it and why I selected a sphere. Also, no one said you had to have hardpoints for weapons. Connect up the exterior drydock to pre-assigned points. aka hardpoints.....

 

[marginaleye]

Gee! I think that's where I was going with it and why I selected a sphere. Also, no one said you had to have hardpoints for weapons. Connect up the exterior drydock to pre-assigned points. aka hardpoints.....

I thought of how one might model the "collapsible dry-dock" (or "work-sheds," or "sausages," or whatever you prefer to call them) using the Book 5: High Guard design system -- treat them as collapsible fuel tanks, carried externally. Their volume, fully deployed and inflated, should be easy to calculate if (a) both the ship's hull and the "dry-dock" are cylindrical, and (b) the "ceiling height" of the deployed "dry-dock" is known and constant along the length of the hull. Once the deployed volume has been calculated, the "packed" volume can be determined by consulting the rules. It's probably a very rough approximation, but then so much else of High Guard is, too.

 

[MrMorden]

As an exploration-lover, I dig these kinds of thought experiments. I think this is a doable enterprise.

IMO the ship should be large and redundant. I'm thinking 100Kton+ size, with multiple powerplants, jump drives (J2+), and maneuver drives. It needs large mechanical and electronic workshops, and lots of engineers. Enough spares to overhaul the drives at least three or four times. It would have to be streamlined enough to skim fuel (fully streamlined to land on oceans for fuel would be ideal), and have multiple fuel purification plants.

It needs to have a lot of small craft, shuttles and cutters. I would probably include a couple of Scout/Couriers to range ahead and make sure the path is safe.

I might also have a large contingent of replacement engineers and scientists as a frozen watch in low berths. You'd really hate to get stuck a couple hundred parsecs from the Imperial border with no mechanics...

Weapons are a secondary consideration in this design. I'd probably go with a few 100 ton PAW bays and some 100 ton missile bays. Equip the ship with a goodly stockpile of nuclear missiles in case things get really ugly.

Route selection should be largely done in advance. Location of systems should be determinable by astronomy, since we can do that now. Locations of gas giants should largely be able to be known. Plot a general course that agrees with the jump performance of the ship.

Allow the scouts to range at least one jump ahead of the mothership, and report back their findings. The mothership will thus only be making around one jump a month, but a lot of systems that are uninteresting or dangerous can be safely bypasses, so the jumps are more efficient. It also gives a full month of survey/exploration time in systems that are of interest.

Andy

 

[The Hinterworlds Rambler]

A most interesting set of ruminations, My Lords...

Could not automation play a role in this venture? Could not the Drydock be brought to the drive?

What of a Jump Drive that is designed to repair and maintain itself? The Drive in question could perhaps have an additional power plant, dedicated to powering a computer that monitors the drive's status and function. "The Drive Computer" could perhaps also have "slave" robotic units that do three things very well...

1. Make Replacement Jump Drive Parts and do the physical labor vital to the Drive
2. Find the Raw Materials for Jump Drive Parts and process them
3. Make Copies of themselves.

This concept would work well on a sizeable vessel with good cargo potential and a very sophisticated onboard fuel treatment plant...

Ahh, but then you have the life support Issue...