## Low tech ships - Need help

Discuss the Traveller RPG and its many settings
AnotherDilbert
Cosmic Mongoose
Posts: 3389
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

### Re: Low tech ships - Need help

DivineWrath wrote: I was listing some of the stats for my ships.
I got that much, I didn't understand the stats:
DivineWrath wrote: I've been working on small craft lately. I've been giving them 4 units of thrust. I picked that number so that delta v is 1 unit.
Thrust is a force, measured in Newton (N); Do you mean what MgT calls Thrust 4 (probably 4 G acceleration)?
delta-v (difference in velocity) properly has the unit m/s, does the craft have 1 m/s ∆v (i.e. very little)?
DivineWrath
Mongoose
Posts: 174
Joined: Fri Mar 28, 2014 10:45 pm

### Re: Low tech ships - Need help

Oh, sorry. I didn't know how to properly say it. I got in the bad habit of saying thrust 4. When I say thrust 4, its 4 * 0.025% of the hull set aside for reaction fuel. So the ship can do 1 G acceleration for 4 hours.

How would you say it?
AnotherDilbert
Cosmic Mongoose
Posts: 3389
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

### Re: Low tech ships - Need help

DivineWrath wrote: How would you say it?
"the ship can do 1 G acceleration for 4 hours" works well.

It can be convenient to note the amount of fuel in Ghours or Gturns. Let's say you have 2 G drives with 3 hours fuel, then you have 2 × 3 = 6 Ghours or 60 Gturns. If you accelerate at 2 G for a turn you deduct 2 Gturns. This way you can easily keep track of how much fuel you expend each turn.

If you want to take off vertically from a planet I would use at least 2 G drives. The gravity of the planet will counteract the thrust from the drive so that if you have 1 G drives and 0.8 G gravity the craft can only accelerate at 1.0 - 0.8 = 0.2 G upwards. If you have 2 G drives you can accelerate at 1.2 G upwards, making the trip much faster and hence using less fuel to get into orbit.
Condottiere
Chief Mongoose
Posts: 6688
Joined: Mon Sep 23, 2013 8:23 pm

### Re: Low tech ships - Need help

[Percentage (Hull Volume)] bunkerage/(thrustxefficiency).
DivineWrath
Mongoose
Posts: 174
Joined: Fri Mar 28, 2014 10:45 pm

### Re: Low tech ships - Need help

I'll use Ghours. Most of the small craft I've designed have 4 Ghours with a thrust 1 reaction drive. I found to get more flight ability would cut heavily into their ability to do other jobs such as cargo or passengers.

I've looked at the 2300 AD books to try to find information for space elevators and space craft that have to function without gravity drives. I've found that a number space craft built to get to orbit have thrust 3 reaction drives with 3 Ghours of fuel.
baithammer
Lesser Spotted Mongoose
Posts: 769
Joined: Wed May 31, 2017 2:21 am

### Re: Low tech ships - Need help

At low tech levels its best to use shuttles and lifters to move things to an orbital dock that houses the "ship" you'll use while in space.
AnotherDilbert
Cosmic Mongoose
Posts: 3389
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

### Re: Low tech ships - Need help

DivineWrath wrote: I'll use Ghours. Most of the small craft I've designed have 4 Ghours with a thrust 1 reaction drive. I found to get more flight ability would cut heavily into their ability to do other jobs such as cargo or passengers.
For interface craft 2 G is highly desirable. You don't need more Ghours of fuel, so it's only 2% of the craft, at worst reduce reaction fuel to 3 Ghours.

As baithammer points out, if you will only travel in space 1 G is quite sufficient.

You might even use an external reusable booster rocket to reach orbit (Breakaway hull) to simulate a two stage rocket.

DivineWrath wrote: I've looked at the 2300 AD books to try to find information for space elevators and space craft that have to function without gravity drives. I've found that a number space craft built to get to orbit have thrust 3 reaction drives with 3 Ghours of fuel.
That should be plenty to reach orbit. You'll probably want more reaction fuel for long-haul routes such as Earth to Mars or Venus.
steve98052
Greater Spotted Mongoose
Posts: 903
Joined: Tue Oct 01, 2013 6:13 am
Location: near Seattle

### Re: Low tech ships - Need help

If we assume a current level of technology, game rules generally don't give realistic results. We can use real rocket science instead. Ground to space is probably best handled with an aircraft launch vehicle that lifts a rocket to the edge of space, where the rocket takes over (and the aircraft returns to the ground). Return requires heat shields, like the ablation shields of early space flight and the reusable tiles of the Space Shuttle. Almost all of every surface launch mass is fuel.

Interplanetary travel has lots of options: chemical rockets, fission thermal rockets, ion drives and similar electric technologies, and light sails.

There is no stealth in combat. Missiles are the only attack. Dodging is the only defense. Throw enough stuff at an enemy and they're dead -- either from catastrophic impact or from fuel exhaustion that leaves them on a long flight to nowhere until their ship equipment runs out of life support.

The rules of low technology space combat are pretty simple, but they're not much fun. Best answer is to fight it out on the ground.

### Who is online

Users browsing this forum: Old School and 28 guests