Author Topic: Determining Engagement Ranges in Space  (Read 1384 times)

0 Members and 1 Guest are viewing this topic.

Offline pyrotech

  • Adept
  • **
  • Posts: 337
  • OIC Points +45/-45
Determining Engagement Ranges in Space
« on: March 08, 2012, 05:01:21 PM »
I've recently been planning a space vehicle encounter for my PCs and was wondering about how to determine the starting engagement range for space encounters. 

Looking at Harp Sci-Fi I see vehicular sensor range increments are 1 light second.  So I was wondering if I should have the pilot or navigator on duty at the time of the encounter make a sensor operations check with the passive -50 penalty for not paying close attention (ie the combat perception penalty).  Then I was thinking of assigning a contact range of 5 RI (5 light seconds) for a result of 100 modified by 1 RI for each 10 points the check is less than 100.  For checks less than 60 I would then halve the contact range for each additional 10 points it was missed by.  Thus a check of 21 would result in the ship detecting the opponent at a range of 1/16th of a light second (just under 19,000 km).  For every 20 points the check is made I would increase the RI by 1.  Thus a result of 178 would result in detection at 8 light seconds (about 2.4 million km).

Due to the reaction mass carried on the ships in my setting and their fusion torch drives I am looking at ships moving around 500 km/s (about 1 hour of burn at 16 Gs).  So using this method that would mean common detection ranges of (50 die roll + 75 skill - 50 passive detection = 75 = 2 RI = 600000 km) 600,000 km.  That would be roughly 600 combat rounds to react.  That is a full 20 minutes. 

What do you guys think of this.  I know other modifies would apply such as the size and emissions characteristics of the target plus environmental conditions.  But how do you think 20 minutes of warning would work in game?  Should I change some of my assumptions or would this work for your group of gamers?

Thanks,

Clint/Pyrotech
-Pyrotech

Offline providence13

  • Navigator
  • ***
  • Posts: 1,944
  • OIC Points +0/-0
Re: Determining Engagement Ranges in Space
« Reply #1 on: March 08, 2012, 07:34:48 PM »
http://www.ironcrown.com/ICEforums/index.php?topic=8883.msg114402#msg114402

Here's a short but interesting discussion on weapons and engagement range.
"The Lore spell assaults your senses- Roll on the spontaneous human combustion table; twice!"

Offline pyrotech

  • Adept
  • **
  • Posts: 337
  • OIC Points +45/-45
Re: Determining Engagement Ranges in Space
« Reply #2 on: March 09, 2012, 05:43:08 PM »
I've been thinking on this issue and am leaning towards changing some things.

1st I think I am going to change the assumed 100 = 5 RI idea to 100 = 1 RI.  This seems more in line with the rest of the rules, plus tightens up the encounter ranges a lot.

2nd I am thinking of changing the encounter range table to:

10     0.001 RI     300km
20     0.0025 RI   750km
30     0.005 RI     1500km
40     0.01 RI       3000km
50     0.025 RI     7500km
60     0.05 RI       15000km
70     0.1 RI         30000km
80     0.25 RI       75000km
90     0.5 RI         150000km
100   1 RI            300000km (1 ls)
120   2 RI            2 ls
140   3 RI            3 ls
160   4 RI            4 ls
180   5 RI            5 ls
280   6 RI            6 ls
380   7 RI            7 ls
...

To make the fractional math easier without a calculator and to make the high end more consistent with the sensor/range rules.

3rd I am thinking about using the 1 minute turn for the initial combat scale which would allow the +20 bonus for turn based sensor operation checks.


The listed weapon ranges in Harp Sci-Fi Xtreme indicate that a small laser would have an effective range out to about .333 ls (100000km) which at the assumed speeds of 500km/s would give typical time to beam range of about 2 turns after detection.  And missile range is all the way out to about 3 ls (a really good detection check). 

So using this set of assumptions most engagements could immediately be shooting matches as soon as the combat started with very little to no cat and mouse maneuvering before the guns start blaring.  As a matter of fact the crews would be very interested in getting to combat stations as quickly as possible just in case the other guy detected them first because they could have missiles inbound already upon detection.

Any thoughts or opinions?

I still need to check what impact reducing the accel of space missiles down to something closer to the slower ships my setting uses.  (10 to 16 Gs is typical for combat vessels - so I am thinking somewhere around 30 to 160Gs for missiles).
-Pyrotech

Offline markc

  • Elder Loremaster
  • ****
  • Posts: 10,697
  • OIC Points +0/-0
Re: Determining Engagement Ranges in Space
« Reply #3 on: March 09, 2012, 09:33:33 PM »
Thinking but I like what I see so far.
MDC
Bacon Law: A book so good all PC's need to be recreated.
Rule #0: A GM has the right to change any rule in a book to fit their game.
Role Play not Roll Play.
Use a System to tell the story do not let the system play you.

Offline providence13

  • Navigator
  • ***
  • Posts: 1,944
  • OIC Points +0/-0
Re: Determining Engagement Ranges in Space
« Reply #4 on: March 10, 2012, 11:29:46 AM »
If I understand your post correctly;
I do like the tighter sensor range increments.

But for beam weapons:
Unless your targets are very stationary, I don't see how light second engagement ranges could work. IMHO, you're and your target still have a minute drift. At those ranges, a little bit off should be a miss.

When I aim a laser pointer at a close object, 3ft. Moving my hand slightly and I might still be near/on target. Using a target 10ft away and a little hand movement may be way off. Aiming at 100ft and a slight movement of the beam could be way off target. But I have shaky hands.  :-[
The hand movement is to represent drift of both vessels.
"The Lore spell assaults your senses- Roll on the spontaneous human combustion table; twice!"

Offline GrumpyOldFart

  • Navigator
  • ***
  • Posts: 1,952
  • OIC Points +0/-0
  • Hey you kids! Get out of my dungeon!
Re: Determining Engagement Ranges in Space
« Reply #5 on: March 10, 2012, 01:07:18 PM »
Yes, but the drift can be calculated if your sensor suite has been reporting the target's movements correctly. However, I'd think that the slower your attack moves (eg. missiles vs. energy weapons), the more likely your foe's sensor suite is to see the attack coming and evade it.

In short, ranges of a light second or more would only be practical for energy weapons. With something like a missile the real range limit would be how much fuel it carries and how fast you can make it use it up. Once it can no longer correct its course to come after you, it's no harder to dodge than any other piece of space junk.

Quote
(10 to 16 Gs is typical for combat vessels - so I am thinking somewhere around 30 to 160Gs for missiles).

The faster it boosts the more fuel it has to carry to go a given distance under power.

This may help:

http://en.wikipedia.org/wiki/Orders_of_magnitude_%28acceleration%29
You put your left foot in, you put your left foot out... Traditional Somatic Components
Oo Ee Oo Aa Aa, Ting Tang Walla Walla Bing Bang... Traditional Verbal Components
Eye of Newt and Toe of Frog, Wool of Bat and Tongue of Dog... Traditional Potion Formula

Offline pyrotech

  • Adept
  • **
  • Posts: 337
  • OIC Points +45/-45
Re: Determining Engagement Ranges in Space
« Reply #6 on: March 10, 2012, 10:59:14 PM »
Yeah the dV is really the limit for missiles and ships in realspace.  In my setting most manned craft have enough reaction mass for hours if not days of burn.  A missile only needs enough reaction mass for a few minutes of burn and that is the limit of its effectiveness.  Once it runs out of reaction mass it can no longer correct and becomes a simple projectile.

I still haven't run the math to check what changing the accel of the missile will do to my engagements. 

The other thing I am a bit worried about is the missiles reaction mass on the launcher.  The fusion torch will be spitting out ionized matter with enough momentum to move a much more massive object at 30+Gs.  The backblast on the missiles will practically be a small plasma weapon to the launcher.  No my setting does have shields to take care of small high velocity particles, but I'm not convinced it will be sufficient to deal with this degree of them.  Maybe I'll just get lucky and my players won't think of this or won't concern themselves with it.

Clint/Pyrotech
-Pyrotech

Offline markc

  • Elder Loremaster
  • ****
  • Posts: 10,697
  • OIC Points +0/-0
Re: Determining Engagement Ranges in Space
« Reply #7 on: March 11, 2012, 12:22:14 AM »
 About missiles you can have them have a timed ignition of their engines so it is ejected from the space craft then after a safe distance the engines kick in full blast.
MDC
Bacon Law: A book so good all PC's need to be recreated.
Rule #0: A GM has the right to change any rule in a book to fit their game.
Role Play not Roll Play.
Use a System to tell the story do not let the system play you.

Offline GrumpyOldFart

  • Navigator
  • ***
  • Posts: 1,952
  • OIC Points +0/-0
  • Hey you kids! Get out of my dungeon!
Re: Determining Engagement Ranges in Space
« Reply #8 on: March 11, 2012, 08:51:47 AM »
Sub-launched missiles are the same way. Blast them clear and let them light off when they are a distance away. One thing you might consider: Fit the missile with a "launch bell" inside the regular rocket bell. Fire a laser up the bell. Your exhaust is vaporized launch bell. When it gets clear or you've run out of launch bell to vaporize, shuck the remainder and only then light off the missile's engine that uses onboard fuel. This will increase range and starting v without adding any more mass to the missile, as your energy source is aboard the launching craft.

Quote
In my setting most manned craft have enough reaction mass for hours if not days of burn.

Yes, but

Quote
(10 to 16 Gs is typical for combat vessels - so I am thinking somewhere around 30 to 160Gs for missiles).

Enough reaction mass for _____ time of burn at 10-16g is one thing. Enough reaction mass for _____ time of burn at 30-160g is another.
You put your left foot in, you put your left foot out... Traditional Somatic Components
Oo Ee Oo Aa Aa, Ting Tang Walla Walla Bing Bang... Traditional Verbal Components
Eye of Newt and Toe of Frog, Wool of Bat and Tongue of Dog... Traditional Potion Formula