Super high speed combat

[SMetze]

I know this has been touched on somewhere, but I couldn't find it after some significant searching.

Issue: So I get how both range band and vector combat would work if both ships say start 50,000km at zero velocity and head toward each other, or one chases the other. Easy. The problem I'm having is something like this: A ship will pop out of Jump into a system, or be out at a gas giant, and then spend say an hour or so at MAXIMUM forward Thrust (let's say Thrust 4 for this argument) toward the main planet, in preparation to then turn around and decelerate again at maximum thrust for the second half of the trip. Then while they are going forward after what would equate to 10 combat rounds at maximum Thrust in one direction, another ship pops up on sensors 50,000 km ahead of them, which has been moving at Thrust 6 for an hour or so to intercept.

That's "Very Long" range. If they both started at velocity 0, they would add Thrust together (because they are moving toward one another) and according to the happy range band chart they would get to the Long range band in 2.5 turns, medium another turn after that, etc. and when they'd get to reasonable ranges they would fight each other.

Except that both ships had a ton of velocity moving from wherever they started to that 50,000km distance and it doesn't just go away. Even if they turn around and start decelerating as soon as they see each other, what keeps them from flying by each other at super high speeds, and going way back out into the range bands for 30 minutes to an hour before they can start to close ranges again? And if they did turn around and both start decelerating, then technically according to the range band method they would immediately start separating and never get any closer to each other.

Standing by for your thoughts.

 

[PsiTraveller]

acceleration rate is ignored and does go away. There is no m/s2 equation. Turn off the M-Drive you stop. Turnover and deceleration is ignored. The 25 g's of acceleration you can get with Mdrives and reaction thrusters don't squish folks either.

Physics makes for difficult combat scenes so it got dropped.

More space opera than hard science fiction.

 

[Reynard]

Did we mention that space, even at the 100D limit, is really, really big. This is why debris in our solar system isn't wiping out the Earth or our orbital craft on a frequent basis. If you get hit by another vessel traveling at high speed in a solar system, it was destined.

 

[Condottiere]

You have to kill velocity to furball; you can do this with very acrobatic manoeuvres, sort of running on the spot, since just showing your behind would tend to make you a sitting duck with a sign saying shoot me.

Smart missiles have the same problem, since if they miss, they have to curve around to reacquire the target.

It's one reason battles usually occur around planetary objects, where there is something worth defending, compared to Weber's assumption to ships passing in the night.

 

[AnotherDilbert]

The problem I'm having is something like this: A ship will pop out of Jump into a system, or be out at a gas giant, and then spend say an hour or so at MAXIMUM forward Thrust (let's say Thrust 4 for this argument) toward the main planet, in preparation to then turn around and decelerate again at maximum thrust for the second half of the trip. Then while they are going forward after what would equate to 10 combat rounds at maximum Thrust in one direction, another ship pops up on sensors 50,000 km ahead of them, which has been moving at Thrust 6 for an hour or so to intercept.

The range band system is very simple and does not model this case.

If you want to model something like this you have to use a vector-based system.

 

[arcador]

Sometimes we play using a vector system and calculating the accelerations.

It involves a player, with an excel sheet, who is a dedicated processor.

It does change the flavour of the battle, as ships tend to "fly past each other" due to the accumulated acceleration.

 

[SMetze]

I appreciate the feedback. I bring it up because a lot of the encounters the players have had so far are similar to this. They arrive from Jump way out away from planet, someone on the planet wants to intercept them, for whatever reason, and by the time they even really get within obvious sensor distance they are both moving so fast they don't have a chance of stopping/fighting/boarding before they whiz right by each other and pause 30 minutes to an hour later and turn to rush back toward each other...

Even a basic planetary patrol ship would be better served waiting until intruders have slowed down to get within planetary striking range than trying to go out, intercept, and follow them in...

And in all cases ships have ended up in combat with their engines facing toward each other.

 

[baithammer]

You have to kill velocity to furball; you can do this with very acrobatic manoeuvres, sort of running on the spot, since just showing your behind would tend to make you a sitting duck with a sign saying shoot me.

Smart missiles have the same problem, since if they miss, they have to curve around to reacquire the target.

It's one reason battles usually occur around planetary objects, where there is something worth defending, compared to Weber's assumption to ships passing in the night.

Smart missiles are the same system as a ship, doesn't require curving around like in an atmosphere. The missile simply pivots like any other vessel and applies thrust toward the new target facing.

As to combat, you need to slow down in order to engage an enemy vessel/fleet and you want to reserve some thrust for defense. ( This is more to the point of why engagements happen around objects.)

 

[Sigtrygg]

Got a blank hexmap that you don't mind writing on and a few counters you can use a ship markers?

If so download the Triplanetary rules from SJG and give them a try out. Once vector based movement is mastered then adapt it to Traveller, or just use Mayday or LBB:2 ship combat.

Here is a link to the rules:

http://www.sjgames.com/triplan/2018rules.pdf

 

[steve98052]

In a situation like that, you probably need to break out the vector rules for any kind of reasonable result. But to keep things simple, just use the vector rules to determine the range band at closest possible range, and then calculate the range bands for the turns immediately before and after the close turn, and if those are not completely out of range, calculate the range bands outside that.

For example, suppose that the closest point is Medium range, the next closest is Very Long, the next is also Very Long, and the next is out of range.

The conflict lasts five rounds, no more, no less, unless someone pushes the Jump button. The first, second, fourth, and fifth rounds are Very Long range, and the third is Medium.

Missile fire is impossible on the fourth and fifth rounds, because the missiles don't have the endurance to catch the adversary, and have reduced chance to hit on the third round due to the precise timing required. But missiles that hit do extra damage.

Lasers (and other directed energy weapons) are do reduced damage in the third round, due to the angular velocity during the pass. They're normal the rest of the time.

Sandcasters require a Pilot roll to be effective in the third round, because the ship needs to pace the "sand" cloud during the pass. They are otherwise normal.

Point defense fire is more difficult in the first and second round, and much more difficult in the third, due to high missile velocity.

Stealth based on electronic countermeasures is more effective during the third round, due to high angular velocity. Passive stealth is unaffected.

How large are the modifiers? Let the game master decide at the beginning of the combat, but adjust if results look ridiculous. Such combats will be very rare because Space Is Big. When they do occur, circumstances will vary enough that it's difficult to define rules for every situation.

 

[Condottiere]

Since the chances are that the targets are constantly in motion, I'm inclined to think that the missiles have to curve to catch up.

The faster you go, the more predictable the path; missiles might have a problem catching up, but once they do, higher likelihood of a successful hit, rather than increased damage.

 

[SMetze]

I was experimenting with spreadsheets and vectors, as you do.

So suppose we have a planet that is 10000km in diameter, which means you have to jump in at about 1,000,000km away or more. Let us also say you are in a ship ("Ship A") with Thrust of 4G. According to the happy rules, it would take you 167 minutes to get to the planet, which I will round up to 168 for math purposes, which translates to 28 combat turns of 6 minutes each.

That means you would be accelerating for 14 combat turns, and decelerating for 14 combat turns. Now, let's say as soon as you arrive in system, a hidden transponder or a stowaway or a distant scouting post transmits your position to the planet. Ship B, also with a Thrust of 4G, sets off from the planet to intercept Ship A. Assuming both ships went full bore towards one another, by the time they reached the midpoint, they would have a vector about 56 "hexes" long. In some math it says a hex is 650km, but in my math it comes out to about 1275km per hex. That means the two ships are now moving at between 36,400km to 71,420km per combat round. Since they are moving toward each other, the relative velocity would be between 72,800km and 142,840km per turn. If neither spun around to slow down at that point, and really even if they did, they could go from Distant range, pass each other close enough to scrape paint, and out to Distant range again in a single combat round without even having time to acquire one another on sensors.

Now, let's say Ship B wanted to attack and Ship A wanted to evade. The best plan for the evading ship is to just not slow down. Keep barreling straight ahead toward the planet, or just continue normal movement toward the planet, decelerating as usual, because even then it will be many turns (like an hour) until the attacking ship can catch up and time that interception right, and by then the attacker would have been better served just waiting at the planet for the defending ship to show up. This makes defending a planet very difficult, because it implies you basically have to wait for the attacker to come to you and get relatively close to the planet before you fight.

I know it sounds like I'm overthinking this, which I have been accused of before, but I like the gritty realism of Traveller, and if real physics creates unusual non-Star Trek non-Star Wars space combat situations and tactics, I want to explore them.

 

[baithammer]

Two limitations that need to be concerned about.

1.) The faster you head to a target the longer breaking period is required, so you end up further from the target.
2.) Going faster than your sensors ability to pickup leaves you with little time to respond to necessary changes.

This is one of the reasons defensive fleets are posted to specific locations, with some patrol ships to pickup in bound traffic.

We now have a new toy with the DSE handbook, which potentially allows us to pickup in system jumps from a longer distance.

GRAVITATIONAL ANALYSIS SUITE TL13

The parsec automatic detection isn't really useful for short term emergence detection, but at shorter distance it can be used to detect deep jump sigs which are attempting to avoid conventional sensors and aren't generally done by legitimate traffic.

The scanner requires a d6x10 hours per parsec or 28,382,191,417,742.4 km at about 3 years delay.

At a distance of about 107,999,206.308 km, it would at the most take a 6 min turn to detect a jump signature. ( Automatic.)

If a 6g ship were to transit towards the Sensor, it would take a little over 55.6 hours so the sensor gives a long time to react.

 

[AnotherDilbert]

Ship B, also with a Thrust of 4G, sets off from the planet to intercept Ship A. Assuming both ships went full bore towards one another, by the time they reached the midpoint, they would have a vector about 56 "hexes" long.

This is not an efficient intercept.

That is one problem with vector movement, the characters are supposed to be skilled in this, the players are generally not...

If you want to intercept Ship A before it reaches the planet you have to accelerate towards it, then slow down and start to accelerate towards the planet again, and finally slow down near the planet again.

The simplest case is to accelerate towards the ship for 7 rounds, decelerate (accelerate towards the planet) for 7 rounds, continue to accelerate towards the planet for 7 rounds, and finally decelerate for 7 rounds.
We get this:

The ships enter Distant range on round 14 and have matched vectors at round 21.

Of course it will not be this simple, the ships will start to manoeuvre as soon as they detect each other, or start shooting. It also ignores that a planet moves with perhaps tens of km/s so will have moved hundreds of thousands of km during this time, and the planets gravity that would accelerate the ships...

 

[AnotherDilbert]

If we take the planets motion and gravity in consideration we get something like this:

We reach the planet on round 28, but note that we have to accelerate at an angle to the planet to make up for the planets velocity, and that the planets gravity start to affect us the last rounds.

To intercept Ship B has to accelerate something like this:

It starts in low orbit around the planet. Note that it is affected by gravity the first few rounds and has to adjust it's acceleration by a few degrees to compensate.

We reach Distant range in round 15 when Ship A is about halfway to the planet and Medium range in round 22 when both ships are about 135 000 km from the planet.

We have to plan the entire movement carefully before we start and it stopped being fun long ago...


Edit:
If we make a plot of the movement:

We start at the bottom at x=0 and move upwards. Each dot is one round.

 

[Welf]

Is it really necessary to take the planets gravity into account? Doesn't the M-Drive accelerate you a fixed amount even though there is a planets gravity affecting you?

 

[Sigtrygg]

Not if you use Mayday/LBB:2/Planetary/Brilliant Lances/Battle Rider...

planetary gravity has to be taken into account if you want any sort of scientific realism, if you go for total fantasy space drives then you can ignore it.

 

[Reynard]

If we want 'scientific reality' then drop maneuver drive concept entirely and only use reaction drive tech.

 

[AnotherDilbert]

Yes, we need to consider gravity.

GRAVITY
The section on planetary templates later in this chapter covers the construction on specific world disks, complete with gravitation bands which can affect movement. When the vector of a ship passes through the gravity bands of a world, the gravity may alter that vector. During the movement phase, lay out the vector of the ship to determine where it will move. If the exact midpoint of the vector lies in a gravity band, a gravity vector will be added to the course vector to create a new vector. The length of this gravity vector is equal (in millimeters) to the strength of the gravity band in Gs x 100. ...

 

[Welf]

An easy way to get an approximation of the number of combat rounds would be easy.

It gets quite complicated and hardly usable at the table if you want to use this kind of combat at the table. "Lets do 20 combat rounds of accelerating and decelerating until you are close enough for combat". Oh and AnotherDilbert already simplified the situation to be in one dimension. And the targeted ship did not change or adjust its course.