Further thoughts about the UES Centauri and the AW space combat environment

[DrTemp]

Well, I could not resist to think more about the Centauri's propellant problem.

 

First, I thought "Okay, it is flight, not cumulative flight, so they'll probably just spend lots of time in free fall." Space battles thus wouldn't be too exciting, but at least it could work, I thought.

 

However, they want to be in orbit around an Earth-sized planet and want to make Hyperjumps from there. The Hyperdrive requires "a distance of about a hundred thousand kilometers" from an Earth-sized world, which means essentially leaving orbit. But to do that, one needs escape velocity- 11.2 kilometers per second. The Centauri with chemical rockets, however, could not hope to carry anything but propellant and manage to reach that speed at the same time.

 

So the obvious solution is another drive, probably a thermal fusion rocket. I am a bit optimistic, so I assume this one has an impulse of about 100 000 seconds, or an exhaust velocity of a about 1 000 000 m/s.

 

That way, our battleship could use only one-third of its 100 ktons of mass as propellant (leaving about 65 000 tons to the actual ship) to have a delta-v of 20% of its exhaust velocity, which means a delta-v of 400 000 m/s or 400 km/s. If it burns all the propellant, which it won't, of course. (100 ktons initial mass divided by 65 ktons final mass is about 1.5, ln of 1.5 is 0.4)

 

This "new and improved" Centauri could accelerate to escape velocity and a bit more, say, 20 km/s, proceed in free-fall to the jump point 100 000 km away (which takes it 5000 seconds, or just below one and a half hours), then jump, decellerate if necessary, accellerate into the other direction again to reach a close orbit, decellerate again, and fight its way through enemy ships. It would then have used up about 20% of its propellant.

 

That's probably as good as it gets with hard SF assumptions. Since we know that Xenovore ships are not far superior to Terran ships, this is probably also close to the technical limits of their dreadnoughts as well.

 

Now what would that imply for ship combat tactics?

 

Most of the time, one fleet will jump into the system, then accelerate (having decelerated before the jump) towards the target planet, where the defending fleet waits in orbit. Detection is absolutely no problem for both sides, since the energy required to power such large ships will be detectable pretty easily via infrared.

 

Intercepting the incoming fleet would not be smart, because that would mean to burn lots of delta-v to get some velocity, then decelerate (with the drive pointing towards the enemy, and no, no Kzinti lesson is applicable here) to match enemy's velocity about the time when the fleets meet each other in space and "escort" the attacking fleet back- if your ships are still in fighting condition after the decelleration maneuver, which the enemy would doubtlessly use to attack you while you can't shoot back accordingly.

 

The defending fleet might manuver a little in orbit, but given the available acceleration rates and delta-v, they won't be able to "evade" any attacks. That means the two fleets will be mindlessly shooting each other, since outmaneuvering is simply impossible. Space combat will thus be a rather boring "who hits most first" excercise.

 

Is this true, or did I overlook anything?

[Longshot]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I'm not that familiar with the AW setting, but I do have Star Hero. Just curious, but in the scenario you described how close would the 2 sides be when they started shooting at each other?

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I would equip the starships with a retractable hydrogen scoop on the front. This scoop would suck up hydrogen molecules and convert them to propellant. This version would give propulsion to about 0.23 c. That would be more than enough to get them outside of the solar system and allow them to kick in the hyperdrive. You could also make it a solar sail if it suits you better.

 

Retractable Hydrogen Scoop: 3" flight Mega-Scale: 1" = 1 million KM: +13/4, Can be scaled to 1KM: +1/4, Costs End: -1/2, OAF: Retractable Scoop, bulky: -11/2. Total Cost: 4

 

Edit to add:

 

9" is 0.70 c

8" is 0.63 c

7" is 0.55 c

6" is 0.47 c

5" is 0.39 c

4" is 0.31 c

3" is 0.23 c

2" is 0.15 c

 

In case anyone wanted to have faster or slower versions.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I'm not that familiar with the AW setting' date=' but I do have Star Hero. Just curious, but in the scenario you described how close would the 2 sides be when they started shooting at each other?[/quote']

 

Well, the Centauri uses Lasers that have MegaRange, 1" = 100km. Same is true for the Xenovore ships. If we assume the crews are rather realistic people, I'd assume they would have to wait/miss until the targets are within some 3200 km or so.

 

Edit: Oh, and relative velocities for an intercept maneuver would probably be well above 10 km/s, while accelleration and decelleration are done with rates of 5-15 m/s^2.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I would equip the starships with a retractable hydrogen scoop on the front. This scoop would suck up hydrogen molecules and convert them to propellant.

 

The available hydrogen in space is not that much, though. And that scoop would have to be very big. Star Hero mentions those Bussard ramjets and what their problems are on page 190.

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

The available hydrogen in space is not that much' date=' though. And that scoop would have to be very big. Star Hero mentions those Bussard ramjets and what their problems are on page 190.[/quote']

I try not to mix too much from Star Hero into AW/TE. It seems that the official world has its own take on how it wants to do things and seems to side-step both SH and TUV most of the time.

 

I remember the Hydrogen Scoop from a 20 year old NASA project and just decided to use it as an example of something that can be utilized both to get 24th century ships out of the solar system so they can employ their hypedrive and also on sleeper-ships in the 22nd century when the colonization process was begun. Of course the Solar Sail, like the one used in the last Star Wars movie, is much cooler looking but for long journeys with a hibernating crew I'd be concerned about sail breakage and then colonists getting stranded.

 

I know your concern is more about vehicle combat but that aspect really does not bother me that much. With the ranges on the ship's weapons they really don't need to get that close.

[Curufea]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

SH is a generic rules set for how things can be run.

TE/AW are setting that use the SH rules for those people who don't want to create their own settings.

SH frequently mentions rubber science - in which category TE/AW falls. So I don't fault it for not obeying the hard science parts also expressed in SH.

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

SH is a generic rules set for how things can be run.

TE/AW are setting that use the SH rules for those people who don't want to create their own settings.

SH frequently mentions rubber science - in which category TE/AW falls. So I don't fault it for not obeying the hard science parts also expressed in SH.

I don't fault it at all. I personally don't believe hard science should be included because most gamers are like me and have no idea what the hard science is. We know Star Trek, Star Wars, Farscape, Andromeda, Firefly, etc. Most games only care about how to get from A to B.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I try not to mix too much from Star Hero into AW/TE. It seems that the official world has its own take on how it wants to do things and seems to side-step both SH and TUV most of the time.

 

Well, in the case of AW, this seems to be rather unintentional. It obviously tries to be hard science where that is applicable.

 

I remember the Hydrogen Scoop from a 20 year old NASA project

 

Do you have a name or link on that? That'd be cool.

 

I know your concern is more about vehicle combat but that aspect really does not bother me that much. With the ranges on the ship's weapons they really don't need to get that close.

 

Well, encounters usually start at a minimum of 100 000 km. Effective weapon range is about 3000 to 5000 km (or is it?). There's a lot of maneuvering one could do to avoid an opponent whose delta-v is a bit scarce...

 

Hm- I'm thinking about the role of space fighters in such an environment. Do they make sense?

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Do you have a name or link on that? That'd be cool.

Sorry, no. It's just a 20 year old memory.

 

Well, encounters usually start at a minimum of 100 000 km. Effective weapon range is about 3000 to 5000 km (or is it?).

The range of mark I lasers is 30,000 km [300" normal range mega-scaled to 1"=100 km]. That is a huge range scope of about 1/12 the distance between the earth and the moon. The range mod for that is about -14 but the size of the Xaeran Tro'Gah is -17 DCV so even at extreme range the Centauri is still +3 OCV to hit. The Xaeran is at -1 OCV to hit due to the Centauri's size.

 

Hm- I'm thinking about the role of space fighters in such an environment. Do they make sense?

I agree fighters can use something to help them close the distance. At 400" per turn they are looking at 30 seconds to close for each kilometer. At 1,000 km they will never reach their targets before everyone falls asleep.

 

A vacuum booster that gives them x8 NCM or more might do the trick though.

[Curufea]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

One of the best space combat systems I've ever seen for realistic physics is Ad Astra's Attack Vector: Tactical. I highly recommend it if you are scientifically inclined

http://www.adastragames.com/products/adastra/av.html

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

The range of mark I lasers is 30' date='000 km [300" normal range mega-scaled to 1"=100 km']. That is a huge range scope of about 1/12 the distance between the earth and the moon. The range mod for that is about -14 but the size of the Xaeran Tro'Gah is -17 DCV so even at extreme range the Centauri is still +3 OCV to hit. The Xaeran is at -1 OCV to hit due to the Centauri's size.

 

I see. That allows for battles at much longer ranges than I anticipated, but I still believe that due to the limited delta-v available even with fusion rockets, the defender's usual tactics should be to wait in orbit and welcome the intruding fleet from there.

 

I agree fighters can use something to help them close the distance. At 400" per turn they are looking at 30 seconds to close for each kilometer. At 1,000 km they will never reach their targets before everyone falls asleep.

 

A vacuum booster that gives them x8 NCM or more might do the trick though.

 

What is a "vacuum booster"?

 

I thought about the fighters, though- in a widely spread formation, they are more capable to withstand a space nuke as a squadron than a larger spaceship the cost of a aquadron is.

 

Fighters would have to be built with a similar fusion drive as the larger ships, though- and maybe about the same delta-v. _If_ one assumes that those fusion drives can be built in such a light way that high-thrust-fusion drives are possible, that is.

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I see. That allows for battles at much longer ranges than I anticipated' date=' but I still believe that due to the limited delta-v available even with fusion rockets, the defender's usual tactics should be to wait in orbit and welcome the intruding fleet from there.[/quote']

I think the tactic would be to have the best hyperdrive pilots that will allow the arriving ship to jump to the furthest possible point to take advantage of range issues. From there the maneuvers would just involve keeping the most distance between the two ships.

 

I agree that ships still need to be able to maneuver. I just think that NCM modifiers on the rockets are just an easier way to handle it. There is already so much DCV modifier due to size that a half DCV from dex will make no real difference.

 

What is a "vacuum booster"?

What I mean by vacuum booster is NCM that only works in the vacuum of space. Imagine the Turbo Boost from the Battlestar Galactica Vipers as an example.

 

Fighters would have to be built with a similar fusion drive as the larger ships, though- and maybe about the same delta-v. _If_ one assumes that those fusion drives can be built in such a light way that high-thrust-fusion drives are possible, that is.

Again, I think the flaw is just that the current rockets have no NCM built into them. This was probably a design flaw that was completely overlooked by everyone

[Zeropoint]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Of course the Solar Sail, like the one used in the last Star Wars movie, is much cooler looking

 

For the record, that was no solar sail. The acceleration of the craft was higher, by a factor or thousands, than what a mere solar sail would provide (especially one that small).

 

Solar sails need to be HUGE and still don't generate much thrust.

 

The official (and only sensible) explanation is that the sail is an old-fashioned hyperdrive system that Dooku uses simply because it IS cooler looking.

 

Zeropoint

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I think the tactic would be to have the best hyperdrive pilots that will allow the arriving ship to jump to the furthest possible point to take advantage of range issues. From there the maneuvers would just involve keeping the most distance between the two ships.

 

Do I understand this right? Both sides should try to keep the distance?

 

BTW, the enormous effect of target size on the DCV implies that it is probably would be best to build ships as small as possible that carry one Mark I Laser (or Xenovore equivalent thereof) each, then take out enemy dreadnoughts/battleships from 30 000 km distance.

 

Interestingly, in the setting description, large ships seem to be the better weapon system. At the moment I just don't see why.

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Do I understand this right? Both sides should try to keep the distance?

Assuming both sides have mark I lasers the smallest ship should always attempt to keep distance between itself and the larger ship. The larger ship is going to want to attempt to close to negate the OCV penalties.

 

I think that most combat is probably fighter to fighter though and then you have a strange dynamic. The carrier ship needs to get close enough to unleash the fighters. The Xaeran hold 50 fighters. The Jupiter only carries 32. It's in the interest of the Xaeran to get close enough to unleash those fighters against the Jupiter, which has limited defenses.

 

BTW, the enormous effect of target size on the DCV implies that it is probably would be best to build ships as small as possible that carry one Mark I Laser (or Xenovore equivalent thereof) each, then take out enemy dreadnoughts/battleships from 30 000 km distance.

 

Interestingly, in the setting description, large ships seem to be the better weapon system. At the moment I just don't see why.

I assume that mark I lasers take up too much space for a smaller craft. That is early technology and probably would require too much area to fit into a ship smaller than size 11 or so.

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

The official (and only sensible) explanation is that the sail is an old-fashioned hyperdrive system that Dooku uses simply because it IS cooler looking.

It doesn't seem logical that Dooku would choose an escape craft using outdated or older technology. He needs to be able to outrun whatever is chasing him. I would guess that they engines are just designed to run more efficiently on solar energy to give the ship the needed edge required to make him faster than everything else; and it did look cool too.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Assuming both sides have mark I lasers the smallest ship should always attempt to keep distance between itself and the larger ship. The larger ship is going to want to attempt to close to negate the OCV penalties.

 

I think that most combat is probably fighter to fighter though and then you have a strange dynamic. The carrier ship needs to get close enough to unleash the fighters. The Xaeran hold 50 fighters. The Jupiter only carries 32. It's in the interest of the Xaeran to get close enough to unleash those fighters against the Jupiter, which has limited defenses.

 

If all participating units have enough delta-v, this could get really interesting. Especially if there's a Centauri guarding the Jupiter... :-)

 

I assume that mark I lasers take up too much space for a smaller craft. That is early technology and probably would require too much area to fit into a ship smaller than size 11 or so.

 

Well, the Centauri is size 20 and has two of them. A ship with half its mass should be able to hold one and would be better off.

 

Edit: Looked it up. The Antarctic class cruiser has size 13 and also has two Mark I lasers... that's only -8 DCV. It also has a better Flight rating. Using the stats as given, that is not good for the Xenovores-

a squadron of them could get really nasty against a Xenovore dreadnought...

 

BTW, I now do believe it makes sense to give the Xenovores not only antigravity, but also reactionless thrusters from the start and let the Liberty class dreadnought be the first human starship with reactionless thrusters, earlier starships having only fusion rockets. Of course, that means early 2300s starships of the United Earth Navy will be hopelessly outclassed by the Xenovores. As it should be.

[Zeropoint]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

It doesn't seem logical that Dooku would choose an escape craft using outdated or older technology. He needs to be able to outrun whatever is chasing him. I would guess that they engines are just designed to run more efficiently on solar energy to give the ship the needed edge required to make him faster than everything else; and it did look cool too.

 

Well, the Star Wars galaxy is supposed to have been at a technological plateau for thousands of years. Just because something is old doesn't mean it doesn't work as well.

 

On the other hand, we seem to be operating on the assumption that the Star Wars universe would make perfect sense if we had all the information. As a work of fiction, that's probably not true.

 

Zeropoint

[MitchellS]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Edit: Looked it up. The Antarctic class cruiser has size 13 and also has two Mark I lasers... that's only -8 DCV. It also has a better Flight rating. Using the stats as given, that is not good for the Xenovores-

a squadron of them could get really nasty against a Xenovore dreadnought...

Yes. That's why it's imperative that the Xenovore dreadnought get within close range. It needs to be able to use it's fighters and railguns. Due to endurance it can't use all 8 of its lasers but if it can use 2-3 of the railguns and 2-3 lasers it can be formitable. I'd like to see a battle between 1 Centuari and 2 Antarctics against a dreadnought. Of course the limited flight issues need to be dealt with first.

[Basil]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

Well, I could not resist to think more about the Centauri's propellant problem.

 

First, I thought "Okay, it is flight, not cumulative flight, so they'll probably just spend lots of time in free fall." Space battles thus wouldn't be too exciting, but at least it could work, I thought.

 

However, they want to be in orbit around an Earth-sized planet and want to make Hyperjumps from there. The Hyperdrive requires "a distance of about a hundred thousand kilometers" from an Earth-sized world, which means essentially leaving orbit. But to do that, one needs escape velocity- 11.2 kilometers per second. The Centauri with chemical rockets, however, could not hope to carry anything but propellant and manage to reach that speed at the same time.

{major snip}

Actually, it won't be a full 11.2 km/s. First, the ship will be in orbit, so it gets the advantage of the velocity it already has. Second, you are not escaping from Earth's surface, but from a few hundred to a few thousand km above it's surface. This is important, because escape velocity depends on one over the square root of the distance (as measured from the center). BTW, escape velocity equals orbital velocity times the square root of 2.

 

So, at ~40,960 km, you are orbiting at ~3.13 km/s, and need to accellerate to ~4.42 km/s, which is a delta-V of ~1.29 km/s. Not much after all, is it.

 

BTW, The Starflight Handbook says fusion rocket engines are expected to have a thrust/weight ratio of ~10^-4 to 10^-5. You won't use much propellent, but you won't get anywhere in a hurry. OTOH, fission rockets will have thrust/weight ratios near to chemical rockets, and much higher exhaust velocities. Light sails, BTW, have very, very low thrust/weight, but of course, no propellent at all.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

So, at ~40,960 km, you are orbiting at ~3.13 km/s, and need to accellerate to ~4.42 km/s, which is a delta-V of ~1.29 km/s. Not much after all, is it.

 

Well, too much for a chemical rocket to do it more than three or four times anyway.

 

BTW, The Starflight Handbook says fusion rocket engines are expected to have a thrust/weight ratio of ~10^-4 to 10^-5.

 

That's based on the assumption that the reactor will be of some Tokamak-related style and that we won't find a lighter way of building up strong magnetic fields. While this is valid for the Starflight handbook's intention, I don't think it will be such a constant as the Tsiolkovski equations.

[DrTemp]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I'd like to see a battle between 1 Centuari and 2 Antarctics against a dreadnought. Of course the limited flight issues need to be dealt with first.

 

I believe "fusion rockets for the Earhters, reacionless thrusters for the Xenovores" should do the job. That would also make the Liberty a _real_ leap forward.

[Captain Obvious]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

One of the best space combat systems I've ever seen for realistic physics is Ad Astra's Attack Vector: Tactical. I highly recommend it if you are scientifically inclined

http://www.adastragames.com/products/adastra/av.html

 

I've thought about picking that up. How is the game play? Is it a game that an average person can enjoy, or do you have to be a physicist to appreciate it?

[Captain Obvious]

Re: Further thoughts about the UES Centauri and the AW space combat environment

 

I'd like to see a battle between 1 Centuari and 2 Antarctics against a dreadnought.

 

Me too. Some of you guys with AW set this up so we can watch.