Calculating STL travel times

[Golan2072]

I'm currently building an alternate Traveller universe where there was a wave of slower-than-light "sleeper" colony ships some time before the invention of Jump Drives. Then things on earth got to hell for som,e time (I know, I know, cliche', but gives the colonies time to develop); I have a general idea of how such ship would be built, but I have several questions in mind regarding this part of my universe's background:

1) How many colonists are required to maintain a healthy gene pool (i.e. how many should be on a colony ship?) What is the rough estimate of cargo tonnage needed for such a colony ship?

2) Assuming early TL9 (but no Jump Drives available yet), with (relatively) advanced computer tech (TL10 or even 11) and a Bussard Ramscoop-fed fusion drive, is there a good formula concerning the time it would take the ship to travel a given distance (10 parsecs minimum, some colonies would be much farther than this)? Remember that the formulas given in CT book 2 are for short distances; a long period of constant acceleration would eventually lead to relativistic speeds, which are annoying to deal with (Mass "increases" as you get closer to lightspeed this effects acceleration and thus complicated the equasion).

EDIT:
3) Is the Bussard Ramscoop needed at all? Assume a constant acceleration of 0.5G, a ship could get to 0.3C (roughly one third of lightspeed) in less than a year. Then it could shut off the engine (which should reduce fuel usage though High Guard doesn't seperate manouver drive fuel usage from power plant output directed to the rest of the ship's systems), until time comes to decelerate on the other side of the journey. This is lower tech, and might be more feasable than the ramscoop, assuming fusion pulse/fusion torch propulsion.

 

[BrennanHawkwood]

Just a quick pointer...some of the info you are looking for may be contained in the following threads. It has been a while since I read them so I'm not certain how closely they address your questions, but they may be a good starting point.

Colony Requirements

Colony Ship Request

 

[Golan2072]

Thanks for the input!

I think I'll go with non-Bussard drive systems - just a fusion pulse (or torch) drive used in the beginning and the end of the jurney for acceleration and deceleration, but shut down for most of the trip.

The computer requirement for hull size is an issue here, atleast according to HG; this could be countered by the fact that my universe has quite advanced computer tech in comparison to other fields (In the early Colonial Era, early TL9 on general, no jump drive yet, but computer tech around TL10, with some devices - especially personal computers, hand computers, HUDs and the like - occur on much lower TLs than in the OTU). Another way to counter this is either by the "networking" as suggested in another thread (once I find the rules for this or build my own houserules) or by "handwavium", that is deciding that the computer cores of the larger colony ships were non-standard, ultra-big prototypes, even though just going realistic would be enough - that is, a small computer produced in 2050 should be able to run a huge astroid-hulled vessel.

Now, my colony ships will come in two classes.
First would be the huge planetoid-hulled Colony Ships of the mid-2050's up to the late 2070's, each carrying 20,000 colonists, enough supplies to start a colony, (comparatively) light armament "just in case" and many smaller craft for the planetary landing and orbital construction once the jurney is over.

In the 2080's IMTU, things began to go bad in the Sol system - political/economic everywhere, the fear of an ecological disaster on Earth (eventually the disaster was much more limited than what was imagined, but that was more than a decade later), problems with Mars' terraformation program and an all-out corporate war in the outer system. Admidst the chaos, some of Earth's more privileged residents sought a way to escape the looming doom. This was why the SeedShips were constructed - small, cheaper interstellar craft, carrying 1,000 colonists each in emergency cryotubes and far less smaller craft; They weren't expected to establish a TL9 civilization, but a more primitive one - TL5 or TL6 - survival was the issue here, not the comfort.

 

[Golan2072]

Originally posted by thrash:
I wouldn't worry about it. Say that the requirement is for ships with tactically useful maneuver drives, and on the scale of High Guard your ships are essentially ballistic.

Thanks - I like your explanation of this matter - and this will save me much annoyances later on. Ofcourse, this also fits with the ship's general concept - it's not intended for small-scale tactical manouvering, anyway. Once in orbit around its target world, the ship will essentially become a big space station, space dock and system-wide base of operations.

 

[aramis]

One thing:

That reaction mass, especially if in the form of "Bagged Ice" (Water inside ballon-like flexible exterior shells), makes a WONDERFUL radiation sink, and even a bit of a microasteroidal buffer!

So, if you do carry it, it's not (IRWT) a waste of mass... Sure, metal is far less weighty for the protection. But, the thing is that metal is single use.

 

[Golan2072]

One more thing... what do you think that a Bussard Ramscoop's stats wopuld be like in High Guard terms?
Especially tonnage and energy usage.

 

[Andrew Boulton]

FF&S has stats, but you'll have to convert to HG.

TL 9
Thrust: 45kN/m3
Mass: 1t/m3
Price: MCr0.85/m3

It needs to accelerate itself up to 1% of c before the 'scoop works, using 0.00035m3/hr/kN of fuel.

 

[ScottB]

Originally posted by Omer Golan:
1) How many colonists are required to maintain a healthy gene pool (i.e. how many should be on a colony ship?) What is the rough estimate of cargo tonnage needed for such a colony ship?

One slightly science fiction-y possibility is to only transport a relatively small number of people - enough to get the colony built and running, and then a few extra - and then a lot of sperm and eggs. Handwave some kind of artificial womb, start growing kids around 15 years before the colony is ready for habitation, and there should eventually be enough people to form a viable gene pool. Make sure the colony ship has plenty of indoctrination - er, I mean training - videos to teach the kids about their heritage, and you could have some pretty interesting colonies by the time jump drive is discovered.

 

[Golan2072]

A very good idea, though artificial gestation should be of a mid-high TL; I think I'll use it to add spice to two of the colony ships, one being built by a consortium of 3 megacorporations (one of them, BioDawn Inc., being a cutting-edge biotech company and holder of the artificial gestation patent), and the other being sent out be a certain religious/"new age"/proto-psionic sect/cult (who stole the blueprints for artificial gestation from BioDawn).
In the first case, indoctrination would be mostly in vid/holo/VR, with some chemical "addetives" added to the childrens' diet; in the second, ceremonies, holy texts (computer-enhanced of course - being a religious cult doesn't automatically make it luddite) and, ofcourse, an early version of telepathy.

Again, thanks for the idea

 

[ScottB]

Originally posted by Employee 2-4601:
Again, thanks for the idea

Any time. I should mention that when it first occurred to me, I was trying to figure out how to somewhat justify Star Trek-style worlds based on particular parts of our past. I'm a sucker for those old episodes where the Enterprise deals with a world of 1920s gangsters or modern-day Romans or whatever, and I figured I could have something like that by postulating a colony built around indoctrination tools provided by a suitably motivated organization, with no direct link to anyone who can tell them which parts of the indoctrination are just propaganda.

So IMTU, I screwed around with tech levels a bit to make automated STL ships carrying nothing but genetic material, the creche/indoctrination system to grow people at the destination, and sufficient robots to build a colony reasonable before jump travel. That way I can have some weird worlds to throw at my players when they go out and explore, based around whatever the ship's builder decided to put in the computer.

 

[Straybow]

"Even so, ramscoop designs are now thought to reach a steady state velocity (well below relativistic effects) where drag on the scoop equals thrust."

Thrash, I think that analysis is based on the assumption of "real" rocket technology. The mass scooped in is the reaction mass ejected, so the steady state is essentially the exhaust velocity (Ve) of the rocket. With a "real" rocket that would limit a ship to maybe 100 km/s. This is handwavium rocket technology.

"0.00035m3/hr/kN of fuel." Hmmmm... what kind of exhaust velocity are they talking about? They're sipping fuel at an amazingly slow rate.

0.00035m³/hr · 1hr/3600s · 1000kg/14m³ = 0.00000694 kg/s

f = ma = dm/dt·Ve = 1kN
Ve = 1kN/(dm/dt)
Ve = (1000kg·m²/s²)/(6.94e-6 kg/s)
Ve = 144.1 million m/s
Ve = 0.48c

That's not an engine, it's a particle beam weapon! Anyway, scooping at 0.48c will provide enough fuel even in the local bubble and rewrites the travel time and survivability equations. You don't need generation crews, just multiple frozen watches to wake up for periodic maintenance.