Space Warships : What if bigger ships are faster?

[PB666]

32 minutes ago, Nuke said:

lessons learned when fusion becomes practical will be able to be directly applied to antimatter containment. by then it might be practical to produce anti matter in large quantities. i just dont want to live anywhere near the antimatter factory.

Which, if you are on the ship, would have to be the antimatter factory on the ship. It takes energy to make anti matter, so that there is no benefit to making antimatter in flight except as a catalyst. 

To go through the process matter antimatter collision make an enormous amount of energy, as much as the mass of the partcles, howvwer when we talk about the energy required for subluminal interstellar travel its not trivial to store. For it to be useful you would have to contain a sizable fraction of the ship mass  in antimatter. 

Its not simply storing anti matter but storing massive amounts infallably for centuries, because once you arrive at your destination you need to decellerate. 

[Windspren]

Plus the reaction "normal" matter. Alcubierre drives FTW! (Yes, I know we need a theory of quantum gravity to prove if it works)

[Pds314]

The counter-argument is of course that nuclear Armageddon can be launched from a ship of practically any size. I really doubt even a capital ship could take a 100 kiloton bomb from point blank and be left in one piece, let alone in a useable state. So you need very effective point defense weaponry on your capital ships. Even a million tonnes of nanotech carbon and maraging steel wandering around the solar system at high speed can be turned to scrap in all of a millisecond if it runs into a 10 kilo chunk of metal.

Edited January 1, 2016 by Pds314

[SomeGuy123]

23 hours ago, Beowolf said:

Well, just off the top of my head, there would be Dr. Robert Forward, James Hogan, and Dr. Jerry Pournelle. Are those the idiots you're feeling superior to?

It's not a matter of superiority.  If they really think it's optimal to carry along the extra mass of the asteroid - the rocks, etc - they really don't know what they are talking about.  It's fundamental engineering.

If Elon Musk, god of engineers, came out and said that corn biofuel was a good idea, I wouldn't have any respect for him, either.  It's a matter of math and facts, and reputation is irrelevant.

Edited January 1, 2016 by SomeGuy123

[Rakaydos]

4 hours ago, SomeGuy123 said:

It's not a matter of superiority.  If they really think it's optimal to carry along the extra mass of the asteroid - the rocks, etc - they really don't know what they are talking about.  It's fundamental engineering.

If Elon Musk, god of engineers, came out and said that corn biofuel was a good idea, I wouldn't have any respect for him, either.  It's a matter of math and facts, and reputation is irrelevant.

I think it's more a matter that the DV gains for a "proper" asteroid sized rocket isnt worth the extra cost, compared to using a bigger, unrefined asteroid and throwing more fuel on it.

[fredinno]

To answer OP, larger ships may have higher top speeds(more overall Delta-V), but smaller ships will have more maneuverability and acceleration- the same size engine can produce more changes in velocity in a shorter time, if the mass needed to move it is smaller. 

[Rakaydos]

1 hour ago, fredinno said:

To answer OP, larger ships may have higher top speeds(more overall Delta-V), but smaller ships will have more maneuverability and acceleration- the same size engine can produce more changes in velocity in a shorter time, if the mass needed to move it is smaller. 

 

 

1 hour ago, fredinno said:

 

Say rather, larger ships are more generally effective, smaller craft are more specialized. A missile might be optimised for TWR, whereas an ion sensor cubest might be optimised for low detectability over combat ranges.

[PB666]

2 hours ago, Rakaydos said:

I think it's more a matter that the DV gains for a "proper" asteroid sized rocket isnt worth the extra cost, compared to using a bigger, unrefined asteroid and throwing more fuel on it.

Hes an id--t, what i originally said was asteroid sized, that aspect would be applicable for both colonizing or offense across interstellar space. an just to point out where he is seriously flawed in his critique, an aggregate mass at the front of a near luminal speed vessel is actual what you want, because collisions with gases and space dust will produce a myiad of particles and radiation which you want to absorb before they are absorbed by your inhabitants, food supply and sensitive electronics. A thin shield of lead does not work when it comes to many elementary particles. The other aspect of an asteroid shaped object is that it might not be recognized as a threat, a death star would be easily recognized as a threat (just make certain that ambient heat ir soectrum is released on the lagging side of the craft). The other thing is that over the course of long space flight there will need to be factories and the raw materials of those factories inevitably come from space dust, in the case of roids alot of nickle iron silicon, ect. As one approaches a target, it might be a good time to begin making short range fighters, or if the enemy is weaker, colonizing or terraforming equipment. 

[SomeGuy123]

5 hours ago, PB666 said:

Hes an id--t, what i originally said was asteroid sized, that aspect would be applicable for both colonizing or offense across interstellar space. an just to point out where he is seriously flawed in his critique, an aggregate mass at the front of a near luminal speed vessel is actual what you want, 

You're a parrot.  You have no idea of what you are talking about or any ability at even basic engineering.  If you did, in roughly 0.1 seconds or less you'd figure out that a random "aggregate" at the front is inferior to a series of precision, repairable armor components, with the exact mix that is optimal for the particle mix you expect to encounter.  Obviously it's a heck of a lot more complex than mere plates of lead.

The other thing you're missing is that if you actually bothered to do the numbers - instead of being a parrot - you'd realize that you're against very terrible fuel constraints for interstellar speeds.  Even with antimatter fuel, getting enough dV for the mission leaves you with pathetic payload ratios, and a centuries long wait.  The damage you face from impact with particles and blueshifted light will require the capability to continually remanufacture the ship, with minimal mass losses.  This is just not a situation where you want to be using something "made from an asteroid".

You would mine the asteroids, no excrements - processing the ore through a series of increasingly stringent purification steps, resulting in probably atomically pure feedstock that would feed into your starship manufacturing shipyard.  You might also ship in raw materials launched from Luna or other Moons and elsewhere - you're going to need a lot of stuff.

Edited January 2, 2016 by SomeGuy123

[PB666]

7 hours ago, SomeGuy123 said:

You're a parrot.  You have no idea of what you are talking about or any ability at even basic engineering.  If you did, in roughly 0.1 seconds or less you'd figure out that a random "aggregate" at the front is inferior to a series of precision, repairable armor components, with the exact mix that is optimal for the particle mix you expect to encounter.  Obviously it's a heck of a lot more complex than mere plates of lead.

The other thing you're missing is that if you actually bothered to do the numbers - instead of being a parrot - you'd realize that you're against very terrible fuel constraints for interstellar speeds.  Even with antimatter fuel, getting enough dV for the mission leaves you with pathetic payload ratios, and a centuries long wait.  The damage you face from impact with particles and blueshifted light will require the capability to continually remanufacture the ship, with minimal mass losses.  This is just not a situation where you want to be using something "made from an asteroid".

You would mine the asteroids, no excrements - processing the ore through a series of increasingly stringent purification steps, resulting in probably atomically pure feedstock that would feed into your starship manufacturing shipyard.  You might also ship in raw materials launched from Luna or other Moons and elsewhere - you're going to need a lot of stuff.

Other than diatribe you have written nothing of any significance here.

[SomeGuy123]

3 hours ago, PB666 said:

Other than diatribe you have written nothing of any significance here.

Says you, which reflects more badly on you than me.  The educated know that 30% efficient at best pion engines are the best known feasible engine at all, and you would need some unknown but probably quite large amount of mass for your antimatter "storage tankage".

 

[fredinno]

GUYS STOP SPERGING OUT

[SomeGuy123]

Sorta sorry.  Just grinds my gears.  If you can hit 5% of the speed of light, the trip to Alpha Centauri takes a century.  10%, it takes 50 years.  An immense difference, even if the crew are immortal, because if you take too long, other faster vessels will beat you there and conquer the place before you ever arrive.

And your rate of acceleration is also a critical problem.  Every time you double ISP, you square the energy required.  This is super bad because when you talk about ultra high ISP engines - the kind of thing that could even reach 5-10% C - you have to release immense quantities of energy for a tiny amount of thrust.  Where does that energy go?  Some of it heats up your engine's magnets and containment walls.  You have to pump that heat out with coolant flow to radiators.  The radiators add mass, lots of it, even if they are droplet radiators you have to have spare coolant.

The TLDR is if you try to pencil it out, you end up with acceleration periods lasting decades or centuries to consume that first 60% or so of the antimatter fuel.  

This is just not a situation where you can afford not to optimize your design in every single aspect, basically down to the atomic level.  

Gregory Benford did have a sci fi story using an asteroid derived starship, but the ship used a ramscoop and thus had infinite fuel.

 

[Beowolf]

On 1/1/2016 at 1:53 PM, SomeGuy123 said:

It's not a matter of superiority.  If they really think it's optimal to carry along the extra mass of the asteroid - the rocks, etc - they really don't know what they are talking about.  It's fundamental engineering.

If Elon Musk, god of engineers, came out and said that corn biofuel was a good idea, I wouldn't have any respect for him, either.  It's a matter of math and facts, and reputation is irrelevant.

You misunderstand me. None of these men seriously proposed such plans. But they all, along with John Varley, Larry Niven, and even Dr. Arthur Clarke, if you think of Rama as a repurposed asteroid, all wrote stories about it...and you called them idiots.

I'd love to hear about the wonders you've accomplished in your life, since these educated, literate, occasionally brilliant men are idiots compared to you. You must hold hundreds of patents! Please enlighten us so I may properly worship you for your mighty achievements.

Or, alternately, you could practice taking a more mature perspective, and realize that 90% of everybody's ideas don't work out, from Einstein to Hawking to you. This just makes them human beings, not idiots. Hell, just months ago, Musk proposed nuking Mars to warm it up, which was absurd once people did the math. But he isn't an idiot; he's a genius who was simply wrong that time.

Incidentally, most SF stories involving large interstellar ships don't use realistic reaction drives. If you had Varley's "bubble drive" from Red Thunder available, your propellant's conveniently stored "elsewhere" having no mass and trivial volume here. So an extra billion tons of asteroid is just cheap radiation shielding.

Ooh, just remembered another one: James Blish's "spindizzy" engines (He wrote the Doomsday Machine episode of original Trek, btw). In those stories, they scooped entire Earth cities out of the ground and turned them into interstellar colonies, including Manhattan island. I never saw much point in that. The magic engines are fine, but wouldn't a colony need far more agricultural space than Manhattan offers? Do we really want an interstellar Wall Street, with trades subject to years of lightspeed lag? Or maybe those empty, useless Wall Street buildings are where the hydroponics will go? Anyway, me disagreeing with him doesn't make him an idiot. It makes him a good author who played "what if" games, and made me think...THAT'S WHAT SF IS FOR.

[ModZero]

On 30 December 2015 at 0:48 AM, SomeGuy123 said:

since nobody can dodge a laser, even a space fighter, at realistic ranges

That's why you don't dodge lasers, but refrain from being predictable and take solace in the light lag. Mind you, that's nothing that would make fighters any better (lasers and even plain old high velocity kinetics would make short-range fights a mess even without a meatbag inside, and fighters don't seem particularly useful outside short range).

On 1 January 2016 at 7:53 PM, SomeGuy123 said:

If Elon Musk, god of engineers

 could do without personality cults. Especially from someone calling other personalities "idiots".

8 hours ago, fredinno said:

GUYS STOP SPERGING OUT

 Y'know,  there're actual Asperger people reading this. Like yours truly.

2 hours ago, Beowolf said:

But they all, along with John Varley, Larry Niven, and even Dr. Arthur Clarke, if you think of Rama as a repurposed asteroid, all wrote stories about it...and you called them idiots.

They weren't idiots (and calling them that is unnecessarily abrasive, and if I say something is too abrasive, that's telling something), they were writers telling stories. The science-ey things in the books made as much sense as was necessary to keep the reader, sometimes a bit more to stroke own egos, but nobody paid them for hyperrealism (nor being super real always feels real, see also amazingly agile spacecrafts and people complaining about E:D behemoths not being agile enough), worse, get too real and you start getting rid of humans from your space exploration. Now that time has passed, the audience got a bit more sensitive, which is perhaps why so much of SF kinda aged less well than fantasy. Point is, SF authors did a lot of wonky science, for many reasons. Them stuffing a ship inside an asteroid isn't really grounds for calling that realistic.

EDIT: gah, sorry, now noticed Beowulf actually was making same point, got lost switching pages. Just replace this with a snarky question about how it's any worse than a non-interstellar wall-street ;-)

 

Edited January 3, 2016 by ModZero

[fredinno]

30 minutes ago, ModZero said:

That's why you don't dodge lasers, but refrain from being predictable and take solace in the light lag. Mind you, that's nothing that would make fighters any better (lasers and even plain old high velocity kinetics would make short-range fights a mess even without a meatbag inside, and fighters don't seem particularly useful outside short range).

 could do without personality cults. Especially from someone calling other personalities "idiots".

 Y'know,  there're actual Asperger people reading this. Like yours truly.

They weren't idiots (and calling them that is unnecessarily abrasive, and if I say something is too abrasive, that's telling something), they were writers telling stories. The science-ey things in the books made as much sense as was necessary to keep the reader, sometimes a bit more to stroke own egos, but nobody paid them for hyperrealism (nor being super real always feels real, see also amazingly agile spacecrafts and people complaining about E:D behemoths not being agile enough), worse, get too real and you start getting rid of humans from your space exploration. Now that time has passed, the audience got a bit more sensitive, which is perhaps why so much of SF kinda aged less well than fantasy. Point is, SF authors did a lot of wonky science, for many reasons. Them stuffing a ship inside an asteroid isn't really grounds for calling that realistic.

EDIT: gah, sorry, now noticed Beowulf actually was making same point, got lost switching pages. Just replace this with a snarky question about how it's any worse than a non-interstellar wall-street ;-)

 

Sorry. I just tried to get you guys to stop arguing.

Edited January 3, 2016 by fredinno

[AeroGav]

Star Wars and Battlestar Galactica are space operas that draw heavily from Naval warfare.  They are based around the Carrier and Fighter since that's the current capitol ship of blue water conflict.   Star Trek harkens to an older era of naval warfare, when the Battleship ruled.  From a storytelling perspective, it allows Luke Skywalker to be a hot shot fighter pilot operating alone, the Star Trek universe is better suited to Captain Kirks and Bill Shatners.

Before people start using real life naval warfare to justify the carrier/fighter model,  you need to remember a few things about terrestial carrier aviation that would not apply to space combat -

1.  The fighter planes are operating in a different medium than the ship - air vs water - one which is orders of magnitude less dense, allowing speeds 30-40 times faster.   In Star Wars, both operate in space, removing one advantage from the fighter.

2.  The curvature of the earth limits line of sight to a few miles at low altitudes, giving a warship very little time to react to incoming fighter/bombers.    In space, line of sight goes to infinity and there is basically no cover at all.   Incoming fighters can be detected and attacked days/weeks out.

3.  Space combat is with directed energy weapons moving at light speed, which cannot be dodged.  On earth, such weapons aren't able to realise their range advantage because of the horizon and atmospheric scattering reduces their effectiveness.  

4. Would the fighters even have enough delta v to close with their target?  

 

 

[SomeGuy123]

13 minutes ago, AeroGav said:

4. Would the fighters even have enough delta v to close with their target?  

That's the point of this thread - they wouldn't, unless you redefine a "fighter" to be the size of a modern day blue water capital ship.  That's because the efficient kinds of engine - fusion, antimatter, orion - all require a much larger and more massive ship to mount them to.

[Alias72]

2 hours ago, SomeGuy123 said:

That's the point of this thread - they wouldn't, unless you redefine a "fighter" to be the size of a modern day blue water capital ship.  That's because the efficient kinds of engine - fusion, antimatter, orion - all require a much larger and more massive ship to mount them to.

Yes if by "fighter" you mean unmanned expendable vehicle with an explosive on the end.

 

 

 

 

 

by which I mean missile. You can make a missile.

 

Bonus: It also doesn't show up to work drunk or forget its lines.

[fredinno]

Can't you still use a NTR, and get a pretty small sized ship with enough Delta-V to go there and back?

[Bill Phil]

In space small craft have less inertia at any given velocity. That's a good thing for some purposes, like maximizing energy per delta V unit, but you don't care as much if you have a different purpose.

[THIRTY9CLUES]

DISCLAIMER: I am not a scientist. I do not claim to be a scientist. I am not anymore related with the terms you are using than the typical Joe across the street. But I love science-fiction and space.

The biggest problem in basicically all of our designs is the fact that targets will be a ways way from your location. For example, if a target where millions of billions of light years away, a satelite based laser wouldn't reach them in a very long period of time. Making them absolutely worthless. If we try to transport a "Fighter" over to that location it would take centuries, even at the speed of the light, to reach it. Now the solution to this is the Alcubierre drive, or some other FTL based drive. However, there is an elephant in the room, to all this disscusion. Where are we on the technological scale. At our current technological ability, none of the energy sources you would imply, Antimatter and Fusion, would not be possible. However, If we are all the way at the end of the technological scale, hitting the absolute of technology, then maybe there are even infinite energy sources with no cooling issues, FTL drives, and the magical "Inertia Dampners".

[Rakaydos]

On 1/4/2016 at 4:18 PM, Alias72 said:

Yes if by "fighter" you mean unmanned expendable vehicle with an explosive on the end.

by which I mean missile. You can make a missile.

 

Bonus: It also doesn't show up to work drunk or forget its lines.

What do you call a missile if you pull out the explosive and replace it with a laser turret?

[linuxgurugamer]

24 minutes ago, Rakaydos said:

What do you call a missile if you pull out the explosive and replace it with a laser turret?

It's still a missle.  Or, possible, a drone

[Elukka]

On 1/3/2016 at 4:48 AM, ModZero said:

That's why you don't dodge lasers, but refrain from being predictable and take solace in the light lag. Mind you, that's nothing that would make fighters any better (lasers and even plain old high velocity kinetics would make short-range fights a mess even without a meatbag inside, and fighters don't seem particularly useful outside short range).

If laser combat takes place at ranges where light lag is significant it has the interesting effect of making maneuverability much more important. Specifically, you want high acceleration and high turn rates. A more maneuverable ship will be harder to hit at a given range, and the range at which hit rates against it approach 100% will be shorter. Against a less maneuverable ship, it would find a range where where its hit rate is much better than its opponent's.

Of course, if the range closes much below one light second, hit rates will rapidly start approaching 100% no matter the target's maneuverability. That means ships that rely on maneuver will have a specific optimum range they'll try to keep. They'll want a low relative speed to their target once in range, and if their opponents are less maneuverable, they'll want the opposite - to get as close as possible to even the odds.

I wanted to come up with a term for a ship that relies on active, intense maneuver at long range to gain an edge over its opponent, as opposed to a ship designed to close the range as quick as possible, and the best I could come up with was... fighter. Gah! Obviously any ship that carries a multi-light second range laser isn't going to be small, but it's sort of a good fit since the ship's defining feature is its reliance on rapid multi-g maneuvering.

Edited January 7, 2016 by Elukka