The 3 kilometer question...

[KerikBalm]

6 minutes ago, Spacescifi said:

You are not limited with FTL travel. Just cool your SVL generator and fly out again. 7 LY max to be safe yeah, but you can SVL again once you cool off.

Good math by the way, but your average reader won't dissect the heat generation with math anyway.Time travel? No. Not doing that. 

But how are you stopping that? otherwise, a savy reader will just ask why they don't use the FTL to timetravel (why do they never do that on Star Trek? except when they do, but then they forget about it, except when they don't and have time police from the future). You rely on the reader's ignorance, or willingness to put aside physical laws. Not having it is like giving characters hand grenades, but the characters never throw them, but instead just place them on the ground and run away, because apparently you can't throw them for some reason, or this *thought just never occurred to anyone in the fictional universe*

Quote

Also, FTL sensors exist. 7 LY range.

...
There actually is a tactical difference between translocation space moving past yoy and just blinking there.

I'll grant you that one if you add in FTL sensors (you hadn't mentioned that before). FTL sensors means FTL communication. FTL communication make time paradoxes even easier to do, as you can now simply be alerted of an event before it happens via FTL communication, without having to undertake accelerating anything of significant mass to relativistic velocities to do time travel.

Quote

Now if you did make a whole fleet of 24 relativstic vessels via black hole and SVL, the homeworld defebse force can send whatever spare vessels it has after you us put a bounty on your head.

Too late, relativistic kill weapons are nigh unstoppable. Keep in mind, to stop them before they release their deadly payload, you need to get within 3 km of them, when they are apparently moving 1 light year per hour.

Also, how do the FTL sensors work, they only detect other vessels doing FTL shenanigans? If so, then launch your relativistic projectile at 8 LY out. The enemy will think everything is fine, you can go about diplomacy and such as usual, while the killing blow is already on its way, starting just 2 presidential terms from complete victory.

Normal sensors won't see anything coming, as the projectile is moving at nearly the speed of light, and no emissions from such a projectile would even be close to strong enough to be detectable until the projectile is a light minutes away... and at 99.9% the speed of light, if it becomes detectable from a distance of 10 light minutes, yo uwon't see the signal until its 0.01 minutes away... ie 0.6 seconds before the planet and everything in the star system go kablooey

Quote

Bobbing and weaving to evade numerous ships at FTL will make your attacks harder to pull off.

The speed of light is 299 792 458 m / s , or 299 792 km / s , lets call it 300,000 km/sec. Your ships go 1 light YEAR per hour. 1 year is 8760 hours, thus your ships in the SVL drive are going 2,626,177,920 km/s. A tiny slight change in direction, and they will easily miss by 3km.

Now, your attacking ships can drop out of SVL at any time, and when packing relativistic velocity, can engage from light minutes away.

This is made even easier by the shift to low speed SVL mode once within 7 light minutes of the planet (easy aiming then), the defenders become speed limited, and also slower than the relativistic ships will be when they drop out of SVL. So you need to stop them at farther than 7 light minutes out... any relativistic weapon 7 light minutes out is going to hit, for sure, your speed limited SVL is too slow to intercept them.

So lets say that 7 light minute sphere is the guaranteed kill zone, if the enemy gets that close, its over for you. (its already over if they prepare their first strike years in advance). So 300,000 km/sec * 7min*60 seconds/min, so a 126,000,000 km radius sphere. A = 4 pi r^2. That is 199,503,699,873,566,229 km² to defend, and you need to get within 3 km as they approach. Each ship is only going to sweep a 28 km² area. See a problem here?

Ooops, its 7 light seconds that they slow down, not 7 minutes, but whatevs... still, you can't let them get within light minutes of the target.

Now I presume your ships are going out at the 1 LY/hour to intercept them, so you should intercept about 3.5 light years out.... trying to get within 3 km 3.5 light years out... that's incredibly precision.

Its also a closing rate of 5,252,355,840‬ km/s, trying to get within 3 km for the intercept. If that comes out to a ratio of 5.71 e-10 you need to get an incredible amount of precision. A slight turn or change in speed (accel or decel) - and you said they can turn,

Quote

SVL navigation is as simple as steering your ship like a plane in space

You only need to "bob and weave" to make them off by a distance of 5.7 e-10x your closing velocity, then you dodge them completely, and easily get within the kill range.

[Spacescifi]

 

 

2 hours ago, KerikBalm said:

But how are you stopping that? otherwise, a savy reader will just ask why they don't use the FTL to timetravel (why do they never do that on Star Trek? except when they do, but then they forget about it, except when they don't and have time police from the future). You rely on the reader's ignorance, or willingness to put aside physical laws. Not having it is like giving characters hand grenades, but the characters never throw them, but instead just place them on the ground and run away, because apparently you can't throw them for some reason, or this *thought just never occurred to anyone in the fictional universe*

I'll grant you that one if you add in FTL sensors (you hadn't mentioned that before). FTL sensors means FTL communication. FTL communication make time paradoxes even easier to do, as you can now simply be alerted of an event before it happens via FTL communication, without having to undertake accelerating anything of significant mass to relativistic velocities to do time travel.

Too late, relativistic kill weapons are nigh unstoppable. Keep in mind, to stop them before they release their deadly payload, you need to get within 3 km of them, when they are apparently moving 1 light year per hour.

Also, how do the FTL sensors work, they only detect other vessels doing FTL shenanigans? If so, then launch your relativistic projectile at 8 LY out. The enemy will think everything is fine, you can go about diplomacy and such as usual, while the killing blow is already on its way, starting just 2 presidential terms from complete victory.

Normal sensors won't see anything coming, as the projectile is moving at nearly the speed of light, and no emissions from such a projectile would even be close to strong enough to be detectable until the projectile is a light minutes away... and at 99.9% the speed of light, if it becomes detectable from a distance of 10 light minutes, yo uwon't see the signal until its 0.01 minutes away... ie 0.6 seconds before the planet and everything in the star system go kablooey

The speed of light is 299 792 458 m / s , or 299 792 km / s , lets call it 300,000 km/sec. Your ships go 1 light YEAR per hour. 1 year is 8760 hours, thus your ships in the SVL drive are going 2,626,177,920 km/s. A tiny slight change in direction, and they will easily miss by 3km.

Now, your attacking ships can drop out of SVL at any time, and when packing relativistic velocity, can engage from light minutes away.

This is made even easier by the shift to low speed SVL mode once within 7 light minutes of the planet (easy aiming then), the defenders become speed limited, and also slower than the relativistic ships will be when they drop out of SVL. So you need to stop them at farther than 7 light minutes out... any relativistic weapon 7 light minutes out is going to hit, for sure, your speed limited SVL is too slow to intercept them.

So lets say that 7 light minute sphere is the guaranteed kill zone, if the enemy gets that close, its over for you. (its already over if they prepare their first strike years in advance). So 300,000 km/sec * 7min*60 seconds/min, so a 126,000,000 km radius sphere. A = 4 pi r^2. That is 199,503,699,873,566,229 km² to defend, and you need to get within 3 km as they approach. Each ship is only going to sweep a 28 km² area. See a problem here?

Ooops, its 7 light seconds that they slow down, not 7 minutes, but whatevs... still, you can't let them get within light minutes of the target.

Now I presume your ships are going out at the 1 LY/hour to intercept them, so you should intercept about 3.5 light years out.... trying to get within 3 km 3.5 light years out... that's incredibly precision.

Its also a closing rate of 5,252,355,840‬ km/s, trying to get within 3 km for the intercept. If that comes out to a ratio of 5.71 e-10 you need to get an incredible amount of precision. A slight turn or change in speed (accel or decel) - and you said they can turn,

You only need to "bob and weave" to make them off by a distance of 5.7 e-10x your closing velocity, then you dodge them completely, and easily get within the kill range.

 

I grant you that catching them at FTL would be tough.

Yet modifications could make it easier, by playing with distance radius, making SVL travel only on a linear path, and requiring time to power up to use the drive each time.

All you have done is shown me how to improve thw drive.

 

I understand your true motive here. To prove that in depth scifi analysis shows up all scifi tech as wanting?

Yes. I was aware of that. I even agree with you there. But that won't stop me.

As for backwards time travel,  not everyone is sold on that actually being true, even if it may look good on paper.

Until it is proven via experimentation that going backwards in time is possible, it will be forever relegated to the reams of paper that become books.

[KerikBalm]

15 minutes ago, Spacescifi said:

Until it is proven via experimentation that going backwards in time is possible, it will be forever relegated to the reams of paper that become books.

Its proven that it would work if FTL works.

Its a direct result of relativity, which is proven.

FTL is not proven to be possible.

[Spacescifi]

2 minutes ago, KerikBalm said:

Its proven that it would work if FTL works.

Its a direct result of relativity, which is proven.

FTL is not proven to be possible.

Well... in fiction you know quite well that not all space opera settings have it.

The reason being that it is not a subject the maker wishes to discuss.

[KerikBalm]

26 minutes ago, Spacescifi said:

Yet modifications could make it easier, by playing with distance radius, making SVL travel only on a linear path,

...

I understand your true motive here. To prove that in depth scifi analysis shows up all scifi tech as wanting?

Well, the problem with that, is that with the ability to drop out of SVL at will, even if its in a linear path, the attackers can drop out of SVL at random intervals. Or if they can alter their speed (why not if speed is changing when close to a planet?), all you have to do is be a little early, or a little late from where they first predicted that you'd be for the intercept, then you get past them.

Linear travel and larger distances can try to paper over the problem, but the problem remains.

My motive here is to get you to think about writing scientific fiction, instead of fictional science.

IMO, it shouldn't be "hard" sci-fi and "soft" sci-fi, but rather scientific fiction (Sci-fi) vs fictional science (fi-sci).

You keep making posts not at all based in science, but coming up with fictional technologies on the basis of fictional science.

Antimatter drives, Orion drives, nuclear-electric propulsion to Europa, etc, such stories could all comport with science as we know it. Scientific fiction.

What I keep seeing here is fictional science.

[Spacescifi]

13 minutes ago, KerikBalm said:

Well, the problem with that, is that with the ability to drop out of SVL at will, even if its in a linear path, the attackers can drop out of SVL at random intervals. Or if they can alter their speed (why not if speed is changing when close to a planet?), all you have to do is be a little early, or a little late from where they first predicted that you'd be for the intercept, then you get past them.

Linear travel and larger distances can try to paper over the problem, but the problem remains.

My motive here is to get you to think about writing scientific fiction, instead of fictional science.

IMO, it shouldn't be "hard" sci-fi and "soft" sci-fi, but rather scientific fiction (Sci-fi) vs fictional science (fi-sci).

You keep making posts not at all based in science, but coming up with fictional technologies on the basis of fictional science.

Antimatter drives, Orion drives, nuclear-electric propulsion to Europa, etc, such stories could all comport with science as we know it. Scientific fiction.

What I keep seeing here is fictional science.

 

The drives we do have do not compete well with the demands of my space opera. So I invent.

Simply put, modern technology cannot fulfill my demands. So I do not bother using it.

As for the SVL, simply by increasing the powering up time for SVL time to 15 hours for your average vessel would make the attacks you describe harder.

Advanced vessels could power up in 5 hours for SVL. Cheaper ones could power up in 30 hours.

Dropping out of SVL cpuld be done rather easily, but going to SVL rewuires,a ship to power up first for it.

Granted, if I allowed scifi cloaks like Star Trek, then whoever had them would dominate.

Edited July 8, 2019 by Spacescifi
Power up

[KerikBalm]

Ok, so if I were a commander in your universe, I would simply mass as many SVL capable units as possible.

They'd be as cheap as possible. All I need to win is 1 more ship than the enemy.

Provided that there's no maneuvering in SVL, and there are FTL sensors, then I suppose intercepts cannot be avoided. Therefore I space ships in my attack force 3.1 km apart. Each intercepting enemy vessel will only drop 1 vessel out of SVL. I only need one vessel to get through. All I need to do is accelerate 1 kg to relativistic velocities, and my whole fleet can use SVL to attain relativistic velocity. I can use SVL to get obscene relativistic velocities (there's a big difference in KE between 0.99c and 0.999c

Since these drives break conservation of momentum, I can also use them as a free energy drive (whatever energy cost you give to them can be overcome by just adding more velocity at already high velocity... similar to the oberth effect. Adding 100 m/s at 1,000 m/s doesn't add nearly as much energy as adding 100 m/s at 10,000 m/s). Anyway, that's a minor thing at this point. The point is that .99999c is easily achievable, .9999999999c is easily achievable too. Basically, if I get a ship to hit anything, it will be like a supernova going off. I can aim at your system's star, any planet, an asteroid... I'm packing a system destroying weapon, perhaps a star cluster destroying weapon if I get enough 9's behind that decimal place.

http://www.projectrho.com/public_html/rocket/spacegunexotic.php#id--Relativistic_Weapons

So... my fleet SVLs to gain relativistic velocity, and every ship made as cheaply as possible is now a super star system destroying weapon. They can take 30 minutes, or 30 days to prepare their SVL drives, it doesn't matter.

Once I send them at you, with them properly spaced, its a 1 to 1 ratio of intercepting ship to my ships. If I have 1 more ship, it gets through and destroys your entire home system.

I don't care if my fleet is wiped out, they are expendable missiles.

This is a complete MAD scenario.

Plus I can put a shaped charge nuke on each of my ships. Drop it out of SVL... I set off the nuke ( http://toughsf.blogspot.com/2016/06/the-nuclear-spear-casaba-howitzer.html ) I don't care if it destroys the firing ship in the process. Your fleet is gone and can't retaliate either.

So.... yea, my fleet composition is just a bunch of as cheap as possible SVL drives, each with a shaped charge nuke strapped to them.

Dropping them out of SVL gets you a casaba howitzer in the face at basically point blank range, and if 1 ship gets through, your star system is doomed.

Ship size is irrelevant, only ship number. The one with more ships destroys more star systems.

This either leads to MAD, where nobody risks war, or a pearl harbor plan where you hope a devastating first strike cripples the enemy's ability to retaliate.

[Guest]

You could do surprisingly well with Alcubierre drive+fusion torches, actually. Gas core NTRs also work. Space Opera is quite possible with those. Dune is a good example of limited space travel that was nonetheless feasible. You did need to take a heighliner between systems, but if there network is developed enough, it's little different from using jumpgates. Or you could fit an Alcubierre drive to every ship, though this has consequences (that said, they can be worked around).

You don't need magic FTL technologies or reactionless drives. Of course, if your goal is "science fantasy" or even going outright Star Wars and doing fantasy in space, magic and all, you can. Sometimes it's just easier to stop trying to explain.  SW never did, except for a while, in the prequels.

For my part, even in my "softest" SF, they have fighter-sized Alcubierre drives and, much more subtly, methods of manipulating magnetic fields that are probably way too good (as in, "making a cloaking device by giving a plasma bubble a structure of an optical metamaterial" good). The latest point pretty much ensures you can have ridiculously good fusion drives, antimatter reactors to power them, tiny radiators that glow blue (magnetic fields don't melt) and space-based plasma weapons.

Edited July 10, 2019 by Guest

[kerbiloid]

12 minutes ago, Dragon01 said:

SW never did, except for a while, in the prequels.

Those chlamydichlorians were weird...

[Guest]

Well, they hadn't come up again, so I suppose the writers learned their error.  

[Spacescifi]

15 hours ago, Dragon01 said:

You could do surprisingly well with Alcubierre drive+fusion torches, actually. Gas core NTRs also work. Space Opera is quite possible with those. Dune is a good example of limited space travel that was nonetheless feasible. You did need to take a heighliner between systems, but if there network is developed enough, it's little different from using jumpgates. Or you could fit an Alcubierre drive to every ship, though this has consequences (that said, they can be worked around).

You don't need magic FTL technologies or reactionless drives. Of course, if your goal is "science fantasy" or even going outright Star Wars and doing fantasy in space, magic and all, you can. Sometimes it's just easier to stop trying to explain.  SW never did, except for a while, in the prequels.

For my part, even in my "softest" SF, they have fighter-sized Alcubierre drives and, much more subtly, methods of manipulating magnetic fields that are probably way too good (as in, "making a cloaking device by giving a plasma bubble a structure of an optical metamaterial" good). The latest point pretty much ensures you can have ridiculously good fusion drives, antimatter reactors to power them, tiny radiators that glow blue (magnetic fields don't melt) and space-based plasma weapons.

 

I am not sure any modern technology is suitable for a setting where vessels can casually descend/ascend from 1g gravity planets. Let alone warp/FTL.

Take NTR for example. What cab you do with it?

Just cruise slowly between the planets. Landing and take off again requires nothing less than an SSTO. Again, hard with modern tech though not impossible if you make it lightweight enough.

Problem is, in space, lightweight stuff we currently have is... not fully protectuve against space radiation. If you want that to be the case, and if you want big business with casual space travel... fiction is necessary.

Edited July 11, 2019 by Spacescifi

[HebaruSan]

Why not pick a setting with physics that fit your desired story mechanics? Pirates in the Age of Sail, or pilots in WW2. You're saying "space" and then throwing out everything about it that makes it unique and interesting.

[Spacescifi]

35 minutes ago, HebaruSan said:

Why not pick a setting with physics that fit your desired story mechanics? Pirates in the Age of Sail, or pilots in WW2. You're saying "space" and then throwing out everything about it that makes it unique and interesting.

Spoken like a true Kerbal player. I am glad you appreciate the intricacies of space travel.

So do I.

I have no intention of throwing it all away.

1. Constant 1g acceleration engines will be a must, only because we have nothing that good for traveling across the void.

2. In spite of what some ardently say, it is NOT aways better to have decks aligned with main engine thrust. Particularly if the vessel only has a scifi 1g acceleration engine that cannot be throttled down. In that case, the only way such a vessel could reach orbit would be by taking off like a plane. Since 1g acceleration can take a ship up to space once it builds up enough forward momentum before flying upward.

3. Rotating roller coaster chairs will be standard for the crew, as that way if the ship is massive and it rotates, they will always face g-force with their backs.

4. The main reason why I do not need decks aligned with gravity is because my FTL method transates both trajectory and speed to match tje vessel"s destination. At a relative dead stop. Constant acceleration engines are mostly good for maintaing an orbit anytime you want. Also for rendezvous and docking.

5. So you see... I have not dumped all the intricacies of space travel. Just some modern limitations that would prevent the scifi from happening  if allowed

Edited July 11, 2019 by Spacescifi

[HebaruSan]

1 hour ago, Spacescifi said:

I have not dumped all the intricacies of space travel.

I wasn't talking about alignment of decks or acceleration.

Think about the elements of a story: characters and their values and relationships, cultures, places, and events. The vastness of space would (will, optimistically) have a profound effect on all of those things. One of the great things science fiction can do is explore what it would be like to live under very different circumstances. Do your characters live in space, or do they live in a version of "space" that's been altered to be more like what we're used to?

On Earth since the 1960s we take for granted that we can travel just about anywhere in a few hours. When some authors consider a Mars trip taking 8 months, they recoil from that novel condition of life instead of embracing it; they concoct torch ships or FTL travel to get things back to "normal" as we now live it. Yet just a century or two back, it took weeks or months to cross the oceans; life is very much livable with long travel times, whether we can imagine it or not. What would it be like if you wanted to visit your aunt and uncle, but they lived twenty light-minutes away in one of millions of O'Neill cylinders? Science fiction could show us, or not.

Similarly FTL communication is thrown in to preserve the habits of mind that phones, television, and the internet have given us, rather than accepting that you have to pause multiple minutes to hear back from someone. What would it be like if humans once again formed discrete cultural bubbles, this time spread across the solar system, bound together by local influence and transmission times?

I don't know if a credible limit has been established for the maximum human population of the solar system, but it must be at least in the trillions. What would it be like to be part of a much, much larger (and older) civilization? How would it affect your attitude toward the whole and what you thought your life was all about? How would you as an individual lay claim to the resources you need?

You're contorting your setting into knots, layering rules upon rules, to come up with a way to travel through "space" with the approximate travel times of a modern jet route. If those are the stories you want to tell, just use actual jets, on Earth. Change your "planets" into the cities they really are and thank me later when you land that big book deal.

[Spacescifi]

11 minutes ago, HebaruSan said:

I wasn't talking about alignment of decks or acceleration.

Think about the elements of a story: characters and their values and relationships, cultures, places, and events. The vastness of space would (will, optimistically) have a profound effect on all of those things. One of the great things science fiction can do is explore what it would be like to live under very different circumstances. Do your characters live in space, or do they live in a version of "space" that's been altered to be more like what we're used to?

On Earth since the 1960s we take for granted that we can travel just about anywhere in a few hours. When some authors consider a Mars trip taking 8 months, they recoil from that novel condition of life instead of embracing it; they concoct torch ships or FTL travel to get things back to "normal" as we now live it. Yet just a century or two back, it took weeks or months to cross the oceans; life is very much livable with long travel times, whether we can imagine it or not. What would it be like if you wanted to visit your aunt and uncle, but they lived twenty light-minutes away in one of millions of O'Neill cylinders? Science fiction could show us, or not.

Similarly FTL communication is thrown in to preserve the habits of mind that phones, television, and the internet have given us, rather than accepting that you have to pause multiple minutes to hear back from someone. What would it be like if humans once again formed discrete cultural bubbles, this time spread across the solar system, bound together by local influence and transmission times?

I don't know if a credible limit has been established for the maximum human population of the solar system, but it must be at least in the trillions. What would it be like to be part of a much, much larger (and older) civilization? How would it affect your attitude toward the whole and what you thought your life was all about? How would you as an individual lay claim to the resources you need?

You're contorting your setting into knots, layering rules upon rules, to come up with a way to travel through "space" with the approximate travel times of a modern jet route. If those are the stories you want to tell, just use actual jets, on Earth. Change your "planets" into the cities they really are and thank me later when you land that big book deal.

 

I actually decided against FTL comms. And I have given thought to civilizations, but my mine are unique in that each one actually has a purpose, and not merely to fill a role of good or bad guy.

Each fictional space faring race has a purpose, and they are aware of what that purpose is.

Humans? They are kind of the oddballs, in that they cannot agree on their purpose, or indeed, many other things. One thing unique to humans that is less common is their brand of religion.

To the point that some alien religions humans view as a joke, given the alien ones seem more about sticking to certain ideals rather than any sort of deity.

 

But travel times by necessity will be shorter since how else can a ship travel anywhere it wants in the universe?

Really, that still won't make it easy. If you're interested, read my last post regarding the deck for spaceships. Taljs about the travel scheme I intend to use.

 

 

[Shpaget]

FTL travel but no FTL comms?

Can you say Pony Express?

[Spacescifi]

Just now, Shpaget said:

FTL travel but no FTL comms?

Can you say Pony Express?

 

Sure.

You really don't need FTL comms or sensors. All you really need for efficient space travel is an FTL drive that translates your speed and trajectory to match your target.

You really do not even need constant acceleration drives, but having them does allow for SSTO's. I like SSTO'S.

[KerikBalm]

1 hour ago, Spacescifi said:

I actually decided against FTL comms.

So unstoppable first strike superweapons are back? Now you don't even need to mass more ships than the defense force has, you just need 1 ship per enemy star system.

Awesome

45 minutes ago, Spacescifi said:

You really do not even need constant acceleration drives, but having them does allow for SSTO's. I like SSTO'S.

You don't need "constant acceleraton drives", where I take that to mean a high acceleration drive consuming a minimal amount of fuel/reaction mass so that acceleration is nearly constant for the required dV/ a "torchship".

Consider the venture star... That wouldn't have been a constant acceleration drive, but it would have been an SSTO. Ditto with Skylon. Ditto For a Falcon-9 with no payload.

For SSTO's, you just need an engine or materials that are a little bit better than what we have currently.

[Guest]

9 hours ago, Spacescifi said:

 

I am not sure any modern technology is suitable for a setting where vessels can casually descend/ascend from 1g gravity planets. Let alone warp/FTL.

Take NTR for example. What cab you do with it?

Just cruise slowly between the planets. Landing and take off again requires nothing less than an SSTO. Again, hard with modern tech though not impossible if you make it lightweight enough.

Problem is, in space, lightweight stuff we currently have is... not fully protectuve against space radiation. If you want that to be the case, and if you want big business with casual space travel... fiction is necessary.

There are NTRs and (GC)NTRs.  And in fact, you can do quite a lot with a normal NTR as well. I suggest you try Children of a Dead Earth. It's a truly realistic space combat simulator, which allows you to design your own engines and weapons, according to physical equations. It is possible to make a methane-fueled solid core NTR with 600s Isp and high TWR. I have designed armored warships that would be capable of SSTO if they had some kind of altitude compensation (though they would have to be refuelled in orbit). It does require incredibly advanced carbon composites because they get incredibly hot (that's how they get their Isp), but I think that's not much of a stretch. There are also gas core nuclear rockets. They were never tested (though Russians came surprisingly close), but they effectively remove Isp limitations of solid core NTRs, running 2000-6000s range. They are possible according to physics. 

As for radiation protection, that is not a problem, either. You can make your ships arbitrarily large by adding multiple NTRs. Also, space radiation is not as bad as many people think. You need a coat of something like lithium-6 (very light) to protect you from neutron radiations, and just a coat of something heavier like lead or tungsten, for gammas. COADE does not simulate radiation, but it's easy to calculate. I have made crew modules that can reduce a point-blank nuclear explosion to background, using 50cm or so of tungsten. I used them on SSTO-capable NTR battleships, which carry ample weapons and armor on top of that. Yes, they're big, about half to one kilometer in length. Civilian ships would be much shorter due to not having armor and weapons, and being able to be wider (warships are needle-like to maximize armor sloping).

With gas core rockets, you can have interplanetary torchships capable of taking off and landing. For space opera, it might be better to have interplanetary FTL (but one that wouldn't work too close to the planet). Then, you could get away with regular NTRs. You can also look into fusion drives, which can be quite efficient, though because they have much lower flow rates, they may have heat issues, unless you go "fusion thermal" route, which probably has similar Isp limitations to NTRs.

Edited July 11, 2019 by Guest

[Spacescifi]

9 hours ago, KerikBalm said:

So unstoppable first strike superweapons are back? Now you don't even need to mass more ships than the defense force has, you just need 1 ship per enemy star system.

Awesome

You don't need "constant acceleraton drives", where I take that to mean a high acceleration drive consuming a minimal amount of fuel/reaction mass so that acceleration is nearly constant for the required dV/ a "torchship".

Consider the venture star... That wouldn't have been a constant acceleration drive, but it would have been an SSTO. Ditto with Skylon. Ditto For a Falcon-9 with no payload.

For SSTO's, you just need an engine or materials that are a little bit better than what we have currently.

 

Not unstoppable. 

My current take on FTL is this:

Galaxy drive: Can translate your trajectory and speed to match any light source in the universe, even if it is old and the object is no longer at that exact spot anymore. However close or far you want you can get to it. The closer you get to your destination the more accurate your translative jumps can get.

Limits: The minimum range you can translate jump to is one lightsecond. This prevents the easy missile/vessel speed boost via translation that you devised.

Constant acceleration drives: Allowed.

Stopping relativistic attacks: Once you translate into a system, the fastest way to get from planet to planet is by translating in vacuum. If you translated above Earth, you would just drop, as your speed and trajectory would match earth via translation. You could launch an attack sure, but a relativistic one shot kill it is not. Assuming you did try to gradually build up speed for a relativistic attack, what's to stop nearby patrol ships from translating to you and fighting you? They could translate right in front of you, unless you had a big shield bubble, but that could translate just outside of that launch attacks from there too.

5 hours ago, Dragon01 said:

There are NTRs and (GC)NTRs.  And in fact, you can do quite a lot with a normal NTR as well. I suggest you try Children of a Dead Earth. It's a truly realistic space combat simulator, which allows you to design your own engines and weapons, according to physical equations. It is possible to make a methane-fueled solid core NTR with 600s Isp and high TWR. I have designed armored warships that would be capable of SSTO if they had some kind of altitude compensation (though they would have to be refuelled in orbit). It does require incredibly advanced carbon composites because they get incredibly hot (that's how they get their Isp), but I think that's not much of a stretch. There are also gas core nuclear rockets. They were never tested (though Russians came surprisingly close), but they effectively remove Isp limitations of solid core NTRs, running 2000-6000s range. They are possible according to physics. 

As for radiation protection, that is not a problem, either. You can make your ships arbitrarily large by adding multiple NTRs. Also, space radiation is not as bad as many people think. You need a coat of something like lithium-6 (very light) to protect you from neutron radiations, and just a coat of something heavier like lead or tungsten, for gammas. COADE does not simulate radiation, but it's easy to calculate. I have made crew modules that can reduce a point-blank nuclear explosion to background, using 50cm or so of tungsten. I used them on SSTO-capable NTR battleships, which carry ample weapons and armor on top of that. Yes, they're big, about half to one kilometer in length. Civilian ships would be much shorter due to not having armor and weapons, and being able to be wider (warships are needle-like to maximize armor sloping).

With gas core rockets, you can have interplanetary torchships capable of taking off and landing. For space opera, it might be better to have interplanetary FTL (but one that wouldn't work too close to the planet). Then, you could get away with regular NTRs. You can also look into fusion drives, which can be quite efficient, though because they have much lower flow rates, they may have heat issues, unless you go "fusion thermal" route, which probably has similar Isp limitations to NTRs.

 

The NTR is notorious for radiative exhaust. I do not know of a safe way to use them on an Earth-like world with regular space traffic. It would defy logic.

Since not are only do they not jive with high tech like FTL translation,  but they are'nt even safe to use on Earth-like worlds.

I know, I know, space infrastructure. Elevators etc.

Problem is... what if it's a new world and they don't have that? What are ya gonna do? Regular fusion or NTR down with SSTO's?

Giving natives and colonists cancer?

That is the best we can do in theory. All the high delta v/high thrust rocket engines I know of, even antimatter, spew out lethal cancer causing rays. 

Making your landing site another Chernobyl.

Edited July 11, 2019 by Spacescifi

[Guest]

1 minute ago, Spacescifi said:

The NTR is notorious for radiative exhaust. I do noy know of a safe way to use them on an Earth-like world with regular space traffic. It would defy logic.

Except that's false. The only NTR type with radioactive exhaust is the open cycle GCNR. You don't have to use this particular technology. Closed cycle GCNRs are half as good when it comes to Isp, but you still get around 3000s. With other types, particularly solid core, radioactivity in exhaust is a sign of a critical engine failure. Sure, this is a risk, and crashing such a large gas core SSTO would possibly be a Chernobyl-level environmental catastrophe (and only Chernobyl-level. It really wasn't as bad as most people think). Solid cores are pretty much safe by default, due to them being, well, solid.

The reason for that is that hydrogen is not affected by neutron activation, since deuterium is stable. Methane is hydrogen plus carbon-12, which might be transmuted into carbon-13, which is also stable. In either case, neutron absorption cross section is so low is that transmutations will be sporadic. Solid NTR exhaust is no more dangerous than that of a regular rocket, while GCNR exhaust is no more dangerous than a blue-hot stream of plasma. 

When you're writing, do make sure you include real science, not "popular science". A whole lot of the latter is outrageously wrong. For many things, especially in terms of nuclear technology (the other part that gets hit hard is medicine), if you ask an actual expert, you'll find out that common conceptions are oversimplified at best, and completely wrong as worst (often, they are oversimplifications of things disproved a decade or two ago).

[Spacescifi]

9 minutes ago, Dragon01 said:

Except that's false. The only NTR type with radioactive exhaust is the open cycle GCNR. You don't have to use this particular technology. Closed cycle GCNRs are half as good when it comes to Isp, but you still get around 3000s. With other types, particularly solid core, radioactivity in exhaust is a sign of a critical engine failure. Sure, this is a risk, and crashing such a large gas core SSTO would possibly be a Chernobyl-level environmental catastrophe (and only Chernobyl-level. It really wasn't as bad as most people think). Solid cores are pretty much safe by default, due to them being, well, solid.

The reason for that is that hydrogen is not affected by neutron activation, since deuterium is stable. Methane is hydrogen plus carbon-12, which might be transmuted into carbon-13, which is also stable. In either case, neutron absorption cross section is so low is that transmutations will be sporadic. Solid NTR exhaust is no more dangerous than that of a regular rocket, while GCNR exhaust is no more dangerous than a blue-hot stream of plasma. 

When you're writing, do make sure you include real science, not "popular science". A whole lot of the latter is outrageously wrong. For many things, especially in terms of nuclear technology (the other part that gets hit hard is medicine), if you ask an actual expert, you'll find out that common conceptions are oversimplified at best, and completely wrong as worst (often, they are oversimplifications of things disproved a decade or two ago).

 

Even if you are correct, rockets require a high propellant to cargo ratio. The only way to reduce it by much is with antimatter.... and antimatter infused propellant exhaust is hardly safe.

My scifi constant acceleration drive does 1g acceleration with no fuel use (vacuum jet). The tradeoff is that it cannot be throttled, it only goes 1g.

You could make a 4g or 10g one, but like the 1g, you cannot change/throttle the acceleration rate.

Edited July 11, 2019 by Spacescifi

[KerikBalm]

13 minutes ago, Spacescifi said:

and antimatter infused propellant exhaust is hardly safe.

Ummmm the exhaust wouldn't be "anti-matter infused", the exhaust would be light... gamma rays specifically (and neutrinos, but nothing practical comes from those, nor any danger).

The problem with antimatter is that its extremely reactive, and storing any large amount is storing a massive bomb.

Lose containment, and hiroshima will look like a little firecraker.

Edited July 11, 2019 by KerikBalm

[Guest]

Actually, antimatter infused propellant exhaust is perfectly safe. All antimatter should be annihilated by the time it leaves the nozzle, otherwise the engine is very badly designed. Depending on the exact kind of antimatter used, you should be able to get close to 100% energy absorbed into propellant. 

For the record: what he's talking about is an antimatter thermal rocket. You infuse a bunch of antimatter into a bunch of propellant, and the result gets ejected from the (likely magnetic) nozzle at a prodigious velocity. If you use methane (probably the best propellant if you need good thrust), then your exhaust are atomic hydrogen and carbon. Of course, it isn't exactly safe, in that it's ultrahot hydrogen-carbon plasma, if you're going for high Isp. You want heat-resistant launch/landing pads, but that goes for any worthwhile rocket engine, really. The only exceptions are air-augmented contraptions that lift off at low Isp, using air as propellant. In fact, if you want low infrastructure planets, this is what you should do. Air as propellant is free, and the overhead added by ducting should be manageable.

Antimatter thermal is actually pretty decent. It's reasonably mass-efficient, can develop high thrust, has no thermal issues if designed properly and it doesn't actually need all that much antimatter to work. It's not really a far-fetched technology, either, though it would take quite an advanced civilization to use them on a regular basis. A properly designed antimatter rocket of that type will have a mass ratio of about 2 for any non-relativistic dV, and could have thrust to spare, as well. Atomic rockets posit the Isp for a plasma core antimatter thermal rocket at about 800 000s with hydrogen, with some 50kN of thrust. This is optimized for Isp. With power 0.2TW, you can trade some of that for thrust by changing propellant to methane. I would expect that to be scaleable.

It's your constant thrust 1G drive, right here. It's no more dangerous than anything else storing and exhausting that kind of energy. The great thing about this principle is, as long as you stick to thrust power and rocket equations, you can give it almost any stats that you want. You don't even need radiators, since the very propellant you're using can take that role.

Edited July 11, 2019 by Guest

[Spacescifi]

27 minutes ago, Dragon01 said:

Actually, antimatter infused propellant exhaust is perfectly safe. All antimatter should be annihilated by the time it leaves the nozzle, otherwise the engine is very badly designed. Depending on the exact kind of antimatter used, you should be able to get close to 100% energy absorbed into propellant. 

For the record: what he's talking about is an antimatter thermal rocket. You infuse a bunch of antimatter into a bunch of propellant, and the result gets ejected from the (likely magnetic) nozzle at a prodigious velocity. If you use methane (probably the best propellant if you need good thrust), then your exhaust are atomic hydrogen and carbon. Of course, it isn't exactly safe, in that it's ultrahot hydrogen-carbon plasma, if you're going for high Isp. You want heat-resistant launch/landing pads, but that goes for any worthwhile rocket engine, really. The only exceptions are air-augmented contraptions that lift off at low Isp, using air as propellant. In fact, if you want low infrastructure planets, this is what you should do. Air as propellant is free, and the overhead added by ducting should be manageable.

Antimatter thermal is actually pretty decent. It's reasonably mass-efficient, can develop high thrust, has no thermal issues if designed properly and it doesn't actually need all that much antimatter to work. It's not really a far-fetched technology, either, though it would take quite an advanced civilization to use them on a regular basis. A properly designed antimatter rocket of that type will have a mass ratio of about 2 for any non-relativistic dV, and could have thrust to spare, as well. Atomic rockets posit the Isp for a plasma core antimatter thermal rocket at about 800 000s with hydrogen, with some 50kN of thrust. This is optimized for Isp. With power 0.2TW, you can trade some of that for thrust by changing propellant to methane. I would expect that to be scaleable.

 

I tend to agree that antimatter infused propellant is awesome.

However it is still a bomb.

My fictional vessel will have a crew of 150, may be 150 meters long, may weigh 9,200 tons and will also have the translation drive, and grav-inverters for falling upward into space.

I could use antimatter thernal rockets, since my spaceships only really need to use their rockets in space.

However with the potential weight I listed, it will burn through propellant, even with antimatter. 

Granted, you could use less propellant for more thrust thanks to antimatter.

I wonder how long it woul last? Probably an hour or so or less?

EDIT: Wow. I think the antimatter may be good enough for several hours if my math is correct.

3600 seconds in an hour. Antimatter thermal has an ISP of 800,000 seconds with hydrogen you say?

800,000 seconds divided by 3600 seconds gives me 222 times. 

That means... 222 hours?! Of thrust?!

That is more than good enough, assuming it could do 1g for hours on end, rather than using less thrust to get better ISP.

Assuming I did not goof up the math royally.

Did I?

Edited July 11, 2019 by Spacescifi
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