Low tech ships - Need help

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AnotherDilbert
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Re: Low tech ships - Need help

Postby AnotherDilbert » Wed Dec 20, 2017 12:44 pm

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
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Re: Low tech ships - Need help

Postby DivineWrath » Wed Dec 20, 2017 3:05 pm

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
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Re: Low tech ships - Need help

Postby AnotherDilbert » Wed Dec 20, 2017 8:01 pm

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.
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Re: Low tech ships - Need help

Postby Condottiere » Thu Dec 21, 2017 5:41 am

[Percentage (Hull Volume)] bunkerage/(thrustxefficiency).
DivineWrath
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Re: Low tech ships - Need help

Postby DivineWrath » Fri Dec 22, 2017 5:13 am

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
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Re: Low tech ships - Need help

Postby baithammer » Fri Dec 22, 2017 5:36 am

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
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Re: Low tech ships - Need help

Postby AnotherDilbert » Fri Dec 22, 2017 11:46 am

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.
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Re: Low tech ships - Need help

Postby steve98052 » Sun Dec 31, 2017 5:53 pm

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.

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