GURPS Spaceships, in use!

[Mark Skarr]

Originally Posted by Tommi_Kovala

Good heavens.

It's not like they spent it over night. That ship took nearly a decade to build in space. $238 billion a year is a lot of money, but hardly the terrifying sum. Okay, considering that NASA's budget request for 2008 is $10.5 billion it's a little out there.

And, according to Wikipedia (where all human knowledge is stored!) the US has a current GDP of $13 trillion.

Don't forget that you're building a "unique" vehicle with highly advanced technology (for modern day). Also on p.34 of Spaceships there's even a section on Cost and limited production runs. Believe me, the Glacier Bay is a one-of-a-kind ship in its world. Her actual cost was $23.8 billion, but I added the x100 limited production multiplier.

Also, the cost of the Glacier Bay was a running gag between my sister and myself when I first built it in 1989. The joke was that the designers of the ship artificially inflated the price of the ship and pocketed the differences. They all retired exceptionally wealthy. In countries without extradition treaties.

[David L Pulver]

Originally Posted by Mark Skarr

It's not like they spent it over night. That ship took nearly a decade to build in space. $238 billion a year is a lot of money, but hardly the terrifying sum. Okay, considering that NASA's budget request for 2008 is $10.5 billion it's a little out there.

And, according to Wikipedia (where all human knowledge is stored!) the US has a current GDP of $13 trillion.

If you really want to blow budgets, go into antimatter fuel!

[Mark Skarr]

Originally Posted by David L Pulver

If you really want to blow budgets, go into antimatter fuel!

I guess, as the designer of the system, you'd also get some kickbacks of that fictional money. ;-)

[DemiBenson]

So, I've got a directed question for any of you:

Without superscience, how do you get a colony ship to Alpha Centauri (requires about 4000 mps delta-V)?

At TL9, it seems impossible - even using a magsail for braking (to save half the delta-V requirement), multi-staging like crazy, an Adv Fusion Pulse Drive, and the Delta-V Increase table on page 27, that still gives only 32 mps per stage... which comes to 63 stages.

At TL10, it comes just into possibility - using the same parameters, you get 160 mps per stage, or 13 stages. If the colony ship (final stage with magsail) is SM+10, the whole vessel would be SM+23 when it leaves the solar system. And let's not even mention the cost...

At TL11, it becomes possible to do - same parameters again, leaves us with only four extra stages necessary. When it leaves the solar system, the colony ship (SM+11) with all its boosters is going to be SM+15 or larger.

Antimatter has higher delta-V, but generally the fuel costs so much more than the efficiency increase, that it isn't worth it. The exception might be Antimatter Pion (3400 mps per fuel tank), which means that the colony ship could get there in a single stage, 2 at the highest. Fuel cost is still astronomical.

So... am I missing anything?

[PK]

I'm still reading the book (I finally bought it), but why would it require 4000 mps delta-V? As I understand it, you only need enough dV to get out of whatever orbit you're in, to acclerate a little, then to decelerate and enter a new orbit (and if you're going slowly enough, you can use the new orbit itself to brake.) So if you're willing to take a very, very long time, there's no need for a lot of dV.

[DemiBenson]

Originally Posted by Rev. Pee Kitty

I'm still reading the book (I finally bought it), but why would it require 4000 mps delta-V? As I understand it, you only need enough dV to get out of whatever orbit you're in, to acclerate a little, then to decelerate and enter a new orbit (and if you're going slowly enough, you can use the new orbit itself to brake.) So if you're willing to take a very, very long time, there's no need for a lot of dV.

Read the last part of the boxed text on page 21. The scenario is: how do you get to Alpha Centauri without superscience (which requires 4000 mps of delta-V)?

[David L Pulver]

Originally Posted by ectropy

Read the last part of the boxed text on page 21. The scenario is: how do you get to Alpha Centauri without superscience (which requires 4000 mps of delta-V)?

4,000 mps is to get to alpha centauri (including braking) at about 1% of light speed in 400 years with braking time. Obviously you can do so more slowly or more quickly...

[PK]

Originally Posted by ectropy

Read the last part of the boxed text on page 21. The scenario is: how do you get to Alpha Centauri without superscience (which requires 4000 mps of delta-V)?

Just read it. It doesn't say that it requires 4000 mps dV to get to Alpha Centauri. It says that it requires that much to do so within 400 years. So the obvious answer to me is to take more time. I'd imagine that you could get by with 1/2 or 1/4 that dV if you were willing to take a few thousand years.

[David L Pulver]

Originally Posted by Rev. Pee Kitty

Just read it. It doesn't say that it requires 4000 mps dV to get to Alpha Centauri. It says that it requires that much to do so within 400 years. So the obvious answer to me is to take more time. I'd imagine that you could get by with 1/2 or 1/4 that dV if you were willing to take a few thousand years.

Most of my generation ship designs putter along about 1/500 of light speed. Be careful you don't exhaust your main power plant, though, and do remember to install either farms or total life support.

[dynaman]

Originally Posted by ectropy

Without superscience, how do you get a colony ship to Alpha Centauri (requires about 4000 mps delta-V)?

Not trying to be snarky, but the only answer that works is Handwavium. It was good enough for the show...