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Old 12-03-2014, 12:13 PM   #1
Varyon
 
Join Date: Jun 2013
Default Space Opera Semi-Psuedovelocity Drives

I'm trying to come up with a drive system (actually, a series of them) for spaceships in a Space Opera setting. As with most Space Opera, the idea is to recreate WWII-style combat, but IN SPAAACE.

First off, I should note that power plants in this setting are limited. Power generation is primarily provided by TL 10 Fuel Cells and MHD Turbines, both of which have the option of using HEDM instead (slightly higher cost, double endurance, Volatile System), and by capacitors (same price as a Fuel Cell, holds 6 PPh). Capital ships often have retractable (carried as cargo) solar panel arrays for recharging (they use it to power a refinery to recover fuel). Nothing else is available to spaceships.

As it currently stands, the idea is for capital ships to use semi-reactionless drives. These utilize hydrogen as reaction mass, but get far more efficiency than is realistically possible. They are slow, but steady. They generate mostly pseudovelocity, but do not have pseudoatmospheric handling.

Fighters, on the other hand, use purely reactionless drives. These burn up far more power, requiring capacitors (which I allow to discharge arbitrarily fast) to keep up, but give much greater speed than the semi-reactionless drives of capital ships. They generate mostly pseudovelocity, and they have pseudoatmospheric handling.

The oddity of these drives is that I want them to have travel-relevant accelerations and top speeds while traveling between planets (they enter hyperspace to travel between systems), but have accelerations and top speeds more like WWII vehicles in atmosphere and during combat. For example, a capital ship might cruise at around 100 mps (going from Earth to Mars in under a week), but in combat may only have Move 2/20 (much like the USS Enterprise CV-6). As noted above, the superscience drives produce mostly psuedovelocity, but the velocity in combat is real. That is, when a fighter booking along at 250 yards per second in combat crashes into a stationary asteroid, it (and the asteroid) suffer the effects of a Move 250 collision.

This oddity is the cause of my first problem - what causes the change from "travel speed" to "combat speed?" The main idea I had was that the drives, when powered up, generate some sort of energy field. When two (or more) such fields interact, they interfere with the operation of the drives, eliminating the pseudovelocity component. Unfortunately, that would also mean you can't have allied vessels traveling within "combat range" of each other - unless there's some way to synch up the fields so they no longer interfere. And yet, if this is possible, should it not be possible to synch up with hostile fields in order to make a daring, high-speed escape? And with the advantages inherent in moving far faster, why wouldn't all ships simply synch up, thereby eliminating the possibility of WWII-style combat? Blargh.

The other problems I'm running into come down, quite simply, to numbers. What should "combat range" (that is, the range at which pseudovelocity shuts down) be - and does the size of the vessels involved influence this? What sort of acceleration, top speed, and power drain (and in the case of semi-reactionless, delta-V) should the drives have? I'd also like there to be a "cruising speed," where the vessel continues moving without having to continuously burn energy (and reaction mass) - what should this be? What sort of relationship should exist between psuedovelocity and true velocity? That is, if a vessel is flying around at travel velocity but then comes within range for combat, what velocity does it start with? Similarly, if a vessel rams into an asteroid while traveling, what is its actual velocity for determining the effects of the collision? I have worked out possible answers to these, which I'll list in the next post, but I'd really like some opinions on how well they are likely to work - and if there are any hidden problems I should be aware of.
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Old 12-03-2014, 12:14 PM   #2
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Default Re: Space Opera Semi-Psuedovelocity Drives

Synchronized Drives: Allowing allied vessels to "form up" and synch their drives is easy enough (it would probably take about a minute or so). The issue that arrives is from if it should be possible to synch up with hostile drives. The easiest answer is "No." With the fact that such synching would be of limited use (after all, they would also be synched with you and could pursue at full speed) and add a lot of complication, I'm just going to stick with this answer.


Combat Range: This is a bit hairier. Ideally, combat range should start outside of the maximum range of the weapons of the largest vessel involved. The problem is, this range can easily be quite long. Fortunately, I've already set blaster bolts as traveling at a mere 500 yards per second, regardless of actual range, so we can actually use some of the guidelines from Tactical Shooting here. There, every full second that passes from the moment of firing until the moment of hitting modifies the attack roll by 1d6-5. Blaster bolts are highly visible, so I'm going to assume that the combination of being able to see the incoming projectile and actively attempting to dodge it automatically sets this to minimum. That means a -20 to hit at 5 seconds, which is probably close enough to impossible - that sets combat range as starting at 2500 yards.

There are, however, two complications here. First off, a lot of battles are going to involve so many incoming bolts you can't really distinguish what's going to hit you and what isn't, so going with averages rather than minima might be more appropriate. 10 seconds gets us to an average of -15, which is still probably close enough to impossible, setting combat range as starting at 5000 yards. The other complication is the turbolaser, which requires a minimum SM to mount as a Major Battery (SM +0 for Orange, SM +5 for Yellow, SM +10 for Green, SM +15 for Blue) and greatly increases the velocity of the blaster bolt (1500 for Orange, 5000 for Yellow, 15000 for Green, 30000 for Blue). This increases combat range more, and does it in a staggered fashion - 15,000 for SM 0, 50,000 for SM +5, 150,000 for SM +10, and 500,000 for SM +15.

Rather than going with weapon ranges, I think instead it will behoove us better to use vessel speed. I'm thinking that two 5-drive fighters screaming toward each other at maximum speed should spend a total of 20 seconds in combat range - 10 heading toward each other, 10 heading away. As each fighter is going to have a top speed of 250 yards per second (see later), that's a combined total of 500 yards per second, or a start range of 5,000 yards.


Drive Performance: One thing I should note here is that both drives actually utilize the same general technology, and both are able to decelerate at zero cost (in terms of energy and delta-V). It's just that you can get really high energy efficiency by ejecting reaction mass, but this doesn't let you go all that fast. This is divided up into Semi-Reactionless (used by capital ships) and Reactionless (used by fighters). For both drives, acceleration and energy consumption are proportional - accelerating at only 10% maximum acceleration requires only 10% as much power as normal.

Semi-Reactionless: For pseudovelocity, I'm thinking 1G, 150 mps delta-V (per tank of hydrogen), and requiring 1 PP (so a typical fuel cell lasts for 24 hours of continuous acceleration - enough to burn through around 3.5 fuel tanks worth of reaction mass). Top speed is 100 mps per drive. For real velocity, each drive grants Move 1/10.

Reactionless: For pseudovelocity, I'm thinking 10G and requiring 18 PP (so a 6 PPh capacitor lasts for about 20 minutes at maximum acceleration). Top speed is 500 mps per drive. For real velocity, each drive grants Move 10/50.


Cruising: Cruising speed is the maximum velocity a vessel can go before it actually requires continual thrust to maintain velocity. Cruising speed is equal to half a vessel's top speed. A vessel that is going faster than this and ceases to thrust at at least 10% maximum acceleration loses velocity at this rate until it drops back down to cruising speed. So, a capital ship with 3 Semi-Reactionless drives has a cruising speed of 150 mps. If the vessel is going at 300 mps (its top speed) and ceases to accelerate, it will lose velocity at a rate of 0.3G until it's back down to 150 mps.


Real vs Pseudo: A hint of this relationship can be seen in the discussion of drives, above. Every 10 mps of pseudovelocity corresponds to a real velocity of 1 yard per second. If a vessel lacks inertial dampers, felt acceleration follows a markedly different pattern, being simply 10% of pseudoacceleration (thus, the pilot of a fighter with 5 reactionless drives feels 5 G's when going at full acceleration).
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Old 12-03-2014, 02:33 PM   #3
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Default Re: Space Opera Semi-Psuedovelocity Drives

I think this idea is really cool and I want to help you develop it, but I'm running on a deficit of brain and it would help if you took all the parts you're soliciting input for and bullet'd them out for us.

The part I managed to wrap my head around was the syncing energy field issue. Easy: the energy fields are dynamic, fluctuate essentially randomly, and it's not feasible for an ordinary ship to maintain sync with another ship's field. Perhaps ships in a fleet can sync their fields to a dedicated technobabble logistics ship ("almost all this vessel's resources are dedicated to the large-area gravitic field manipulation necessary to maintain synchronicity" etc) in order to fleets to fly fast in formation. There might even be an expensive/large/energyhungry module that normal ships can install to do this on the fly, including doing it with enemy ships.
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Old 12-03-2014, 02:45 PM   #4
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Default Re: Space Opera Semi-Psuedovelocity Drives

Synched ships must move with the same vector of velocity, and cannot resynch for some while after changing direction. Thus, they move at the speed and acceleration of the slowest ship, and cannot manoeuvre. Even getting close to a gravity well will break the synch due to slightly different effects on the vectors of different ships.

That's how I'm planning to do it if/when I make a Space Operah.
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Old 12-03-2014, 03:15 PM   #5
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Default Re: Space Opera Semi-Psuedovelocity Drives

Alright, so here are the bits I need input on:
  • The how's and why's of ships switching from travel speeds (measured in tens to hundreds of miles per second) to combat speeds (measured in tens to hundreds of yards per second)
    -Addendum to the above, if using "Combat Range," what should this start at?
  • The statistics (acceleration, PP-drain, delta-V, top speed) the drives should have
  • If there should be a speed beyond which constant acceleration is necessary to maintain (that is, a cruising speed that is below top speed)
  • The relationship that exists between the vessel's pseudovelocity and true velocity
  • Potential problems with the setup in general, as well as with my proposed solutions to the above

Quote:
Originally Posted by McAllister View Post
The part I managed to wrap my head around was the syncing energy field issue. Easy: the energy fields are dynamic, fluctuate essentially randomly, and it's not feasible for an ordinary ship to maintain sync with another ship's field. Perhaps ships in a fleet can sync their fields to a dedicated technobabble logistics ship ("almost all this vessel's resources are dedicated to the large-area gravitic field manipulation necessary to maintain synchronicity" etc) in order to fleets to fly fast in formation. There might even be an expensive/large/energyhungry module that normal ships can install to do this on the fly, including doing it with enemy ships.
That could work, but doesn't really fly with what I want - when a pair of fighters launches to engage an enemy outside of combat range, I don't want them to have to drag along some sort of logistics ship to pull it off. I've also decided that being able to synchronize with hostile ships conflicts with the type of combat I want (synchronizing means you will end up fighting each other at travel speeds, which I don't want). If you want (some of) the technobabble explanation, the nature of the disruptive field is easily modified, so it's actually pretty easy to synch up with another ship - but it's even easier to notice that another ship is attempting this, and preempt them by remodulating the field, rendering their modification null. This is so simple it has been automated, and synching up basically consists of all the pilots involved telling their computers "Hey, I want to synch up with these guys," so that the computers synch up and don't remodulate when they notice the other ships doing the same.

Two solutions other than the "combat range" option do come to mind - one is that superscience force screens don't function at travel speed, the other that ships can pretty much only travel in straight lines when using pseudovelocity. I think both will lead to paradigms I don't like - for the former, it means the Evil Empire can field unshielded fighters that function by making Fast Passes on their targets (rather than engaging in dogfights with them), while for the latter it means capital ships - which don't maneuver all that well to start with - have no good reason not to stick with pseudovelocity, leaving those enemy fighters that try to get all WWII on them in the dust. Honestly, I think "Combat Range" is going to work best, but I'm open to suggestions.

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Originally Posted by vicky_molokh View Post
Synched ships must move with the same vector of velocity, and cannot resynch for some while after changing direction. Thus, they move at the speed and acceleration of the slowest ship, and cannot manoeuvre. Even getting close to a gravity well will break the synch due to slightly different effects on the vectors of different ships.
This screws up fighters being launched from a moving carrier. When a carrier cruising along at 100 mps launches fighters, I'd like them to start at 100 mps and be able to break away to engage their targets, rather than requiring everything to drop to a crawl and have the fighters limp away until they're out of the carrier's combat range.
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Old 12-03-2014, 03:47 PM   #6
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Default Re: Space Opera Semi-Psuedovelocity Drives

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This screws up fighters being launched from a moving carrier. When a carrier cruising along at 100 mps launches fighters, I'd like them to start at 100 mps and be able to break away to engage their targets, rather than requiring everything to drop to a crawl and have the fighters limp away until they're out of the carrier's combat range.
Are you sure you want fighters to be able to do that? Because if fighters can, then so can missiles - on a flyby!
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Old 12-04-2014, 06:41 AM   #7
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Default Re: Space Opera Semi-Psuedovelocity Drives

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Are you sure you want fighters to be able to do that? Because if fighters can, then so can missiles - on a flyby!
Yes, I'm certain. If fighters traveling at travel speeds launch missiles, I have no issue with said missiles starting with the same speeds as the fighters. Note that once they come within 5,000 yards of their target, they'll slow down to combat speeds, so the target will still have several seconds to shoot them down (if the target has turbolasers, it may be able to shoot them down while they're still using travel speeds). I still need to work out the particulars of missiles, but I'm thinking they'll probably have ~half their mass in the form of reactionless drives, giving them Move 100/500.

Of course, missile barrages aren't a viable option in this setting. The shields involved are extremely good at stopping dummy-fired missiles, and only remotely-piloted ones stand much of a chance, limiting gunners to one missile at a time (good pilots can actually control a missile and their own ship at the same time without issue, exceptional ones can control two - or occasionally more - missiles and their own ship).

Last edited by Varyon; 12-04-2014 at 12:13 PM. Reason: Had missiles with Move 100/5000, which was inaccurate
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Old 12-04-2014, 08:09 AM   #8
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Default Re: Space Opera Semi-Psuedovelocity Drives

So, I've realized some of the problems with my current setup. First off is the viability of reactionless drives for travel - a single capacitor gives something like 73 mps delta-V, which is below the cruising speed for a single drive (250 mps) and pretty solid for travel. A vessel with a reactionless drive, a capacitor, and an MHD turbine could drain the capacitor in 20 minutes for 73 mps, recharge it over the course of the next 3 hours, boost for another 20 minutes for 146 mps, and then recharge it over the course of the next 3 hours and coast, with a full capacitor and 6 hours left in their MHD turbine. That's really good for travel, particularly compared to a ship with a semi-reactionless drive, a fuel tank, and a fuel cell. In that case, you're looking at over two hours just to get to the cruising speed of 50 mps, at which point you have a 2/3rds full fuel tank and a fuel cell with under 22 hours left in it. You're also traveling at around a third the rate of the reactionless drive.

My solution would be to not have reactionless drives have a cruising speed - regardless of current velocity, you're constantly shedding it at 1G (I'll also get rid of the "unless accelerating at x" bit). In the case of our ship above, that means it's actually boosting at a maximum of 9G (10G - 1G), so it gets up to around 66 mps by draining a capacitor. That MHD turbine provides enough power for 10/9G - call it 1G, but lasting for 13 hours, 20 minutes instead of 12 hours. So, the ship can travel at a respectable rate of 66 mps for this time, but then decelerates at 1G for the next 3 hours, after which point it comes to a dead stop. In total, that means the ship has traveled, over the course of a little under 17 hours, 0.036 AU, or 3.4 million miles - which in space isn't enough to do much beyond traveling between moons and orbital colonies. As the semi-reactionless drive does have a cruising speed, it can spend 2.275 hours boosting to 50 mps, then coast indefinitely. In the same time it takes a reactionless drive to travel 0.036 AU, the semi-reactionless only manages around 0.028 AU - but it will catch up in about 4 hours, then pass the dead-stopped vessel and continue on its merry way.


Another potential issue is at the transition from real velocity to pseudovelocity. Simply reversing the equation - such that a fighter moving at 50 yards per second boosts to 500 mps - means the best way to build up speed is to desynch ships, get up to maximum velocity (over the course of 10 seconds for semi-reactionless, 5 seconds for reactionless), then synch back up. This would be particularly useful for fighters with their 500 mps/drive top speed!
The solution here is pretty easy - once pseudovelocity has been stripped by entering combat, it's gone, and you have to build it back up. So, the fighter moving at Move 50 who exits from combat range stays moving at a piddling 50 yards per second, and needs to build back up to a proper travel speed. Once such a fighter engages pseudovelocity, it actually automatically "dumps" most of its real velocity - it now has a pseudovelocity of a mere 50 yards per second.


I also need to work out exactly how I want energy supplies to work. I'm thinking of actually dumping the purely electrical capacitors and replacing them with HEDM-using systems. Capital ships would use fuel cells or MHD turbines for their drives and those with lots of weapons would probably have an HEDM power plant (beneath heavy armor - send a boarding party to blow it up) to keep them running. Fighters would need an HEDM power plant (hit it and BOOM) for their drives and weapons. I'll have to give it some thought.
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Old 12-04-2014, 08:56 AM   #9
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Default Re: Space Opera Semi-Psuedovelocity Drives

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Yes, I'm certain. If fighters traveling at travel speeds launch missiles, I have no issue with said missiles starting with the same speeds as the fighters. Note that once they come within 5,000 yards of their target, they'll slow down to combat speeds, so the target will still have several seconds to shoot them down (if the target has turbolasers, it may be able to shoot them down while they're still using travel speeds). I still need to work out the particulars of missiles, but I'm thinking they'll probably have ~half their mass in the form of reactionless drives, giving them Move 100/5000.

Of course, missile barrages aren't a viable option in this setting. The shields involved are extremely good at stopping dummy-fired missiles, and only remotely-piloted ones stand much of a chance, limiting gunners to one missile at a time (good pilots can actually control a missile and their own ship at the same time without issue, exceptional ones can control two - or occasionally more - missiles and their own ship).
Well, sure, but this way you can launch all of your missiles on your way to the enemy. Are you still missiles are that useless without manual guidance? How do shield work that it matters whether a missile is guided or homing?
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Old 12-04-2014, 09:29 AM   #10
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Default Re: Space Opera Semi-Psuedovelocity Drives

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Well, sure, but this way you can launch all of your missiles on your way to the enemy. Are you still missiles are that useless without manual guidance? How do shield work that it matters whether a missile is guided or homing?
I still need to work out the specifics, but shields "flicker" in a semi-random pattern, and will pretty much manage a full stop of anything that hits it while it's "on." Thanks in part to the neural interfaces used for piloting, the human mind can subconsciously figure out the pattern to these flickers and strike at the right moment that something actually manages to make it through. Thus, guided missiles can make it at least partially past the shield to explode and damage/destroy the target, but homing missiles are far, far more likely to just hit the shield and be stopped outright. Guided missiles also have the advantage of being able to Dodge point-defense fire, while homing missiles are rather likely to get annihilated.

That's all technobabble, of course. The real story is that I want fighters that use guns and/or blasters for thrilling dogfights, and I want missiles to be singular but serious threats to allow for the pilot to "shake them off" with extreme maneuvers of various flavors.
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