Higher time warp and hibernation instead of magic, unrealistic "warp drive o.O".

[MRab2]

You get 6,7 Newtom by gigawatt, This mean 1 pod at 1G equal to 1 TW. To get this amount of energy you will need aprox 5 km2 of photovoltaic cells made of graphene, very thing very light at middle distance between sun and mercury.

Of course, meanwhile you finish to build that, you can sell the energy to the planet.

And here, as promised, is the shooting down –

1 terawatts of power is short of the requirements by around about a factor of 1000. Let’s run through some numbers.

Let’s assume our intersteller spacecraft weighs 1000 tonnes. Given the ISS weighs around 500 then seems light but we’ll go with it. Let’s assume, again for convenience the top speed of the space craft will be 0.5C. So, knowing these two things we can calculate the ship’s kinetic energy. Which comes out at 1.13x10^22 joules. All that energy has to be pumped into the system via the beam and let’s say we want to accelerate the ship over the course of six months.

That means the beam’s output will be around 706 terrawatts – and that’s assuming perfect absorption by the spacecraft.

Now, at Earth orbit (I know you talked about placing it between Mercury and the Sun, but that would be silly – radiation would make servicing them difficult) solar energy is around 1.3kj per square metre. So let’s plug that in and see how big this mirror thing needs to be – Ok, I’m getting 543,000 square kilometres. If we built it in one big circular piece (which again, would be silly) it would have a diameter of 800 kilometres.

If its average weight per square metre were the same as 80gsm paper (probably what’s in your printer) the whole structure would weigh over 33,000 tonnes. Of course, it’s total mass would be much, much more as you’d build the system out of thousands of smaller mirrors, all with their own control and focusing systems.

If we start accounting for inefficiencies in the system then the actual power requirements could double or even treble, so we could be talking about 1 million – maybe 1.5 million square kilometres of mirror. But we’ll put that to one side and turn to the solar sail.

So we have 700 terawatts of energy pouring in to our solar sail, which unlike our mirror array WILL have to be built as one big structure. Now, even if the sail converts 90% of the incoming energy directly to kinetic energy that still leaves 70 terawatts that’ll manifest as heat which will have to be dumped. What does this amount of energy look like? Well, the Little Boy atomic bomb released 52Tj of energy – our ship is going to have to dump more than this every single second the beam is on it.

This is NOT walking across the room to open a door, this a herculean effort involving, shuffling megtonnes of material around space and numerous technologies that simply aren’t close to existing, and in reality could represent the hard way of doing thing. By comparison, warping space might be a walk in the park.

The tests being carried out on the Alcubierre drive are testing the maths, and the maths suggest the power requirements are much, MUCH lower than the numbers talked about above.

But you forgot to add that alcubierre drive also breaks many other physics rules like cause and effect and some others.

So we need a new physics just to see if can be possible or not. And even if is possible, the amount of energy that will need it will makes pointless the practical use, even if we are a GOD civilization.

Uh, no. The proposed Alcubierre drive does NOT break physics. We know space can expand and contract and we know it's not limited to the speed of light and the reason there's a big hoo-hah about it at the moment is because the maths being tested suggest realistic energy levels are required. Far more realistic than the solar sail model above.

[Scoundrel]

The warp drive/Alcubierre drive is no more realistic than the solar sail. The only difference is that the solar sail can and has been done with current tech... but the engineering to propel a manned spacecraft to another star within a human lifetime using solar sails still isn't feasible, and may never be, for a whole host of reasons (some of which MRab2 has pointed out). Thus it still requires some handwavium to work within the game.

As for the Alcubierre drive, currently it requires lots of handwavium and lots of unobtanium to function:

This is Miguel Alcubierre's twitter response to Sonny White's work.

Then there's this interesting paper on how it would destroy/irradiate anything it's heading towards.

Now, I'm not saying it's impossible or that it will never happen. Rather, I am just pointing out that there is nothing as of yet that confirms that it's possible let alone practical. It is still very much in the realm of theory, without a single experiment that confirms that such a drive could actually be built. Of course that could change in the next couple of decades, I won't argue that, but I think it's likely beyond the scope of KSP if HarvesteR is sincere about avoiding speculative technologies, even if he is a fan of Alcubierre.

[MRab2]

The warp drive/Alcubierre drive is no more realistic than the solar sail. The only difference is that the solar sail can and has been done with current tech... but the engineering to propel a manned spacecraft to another star within a human lifetime using solar sails still isn't feasible, and may never be, for a whole host of reasons (some of which MRab2 has pointed out). Thus it still requires some handwavium to work within the game.

As for the Alcubierre drive, currently it requires lots of handwavium and lots of unobtanium to function:

This is Miguel Alcubierre's twitter response to Sonny White's work.

Then there's this interesting paper on how it would destroy/irradiate anything it's heading towards.

Now, I'm not saying it's impossible or that it will never happen. Rather, I am just pointing out that there is nothing as of yet that confirms that it's possible let alone practical. It is still very much in the realm of theory, without a single experiment that confirms that such a drive could actually be built. Of course that could change in the next couple of decades, I won't argue that, but I think it's likely beyond the scope of KSP if HarvesteR is sincere about avoiding speculative technologies, even if he is a fan of Alcubierre.

All valid points, and if HarvesteR is sincere then that's pretty much it for extra-Kerbol systems as there's no real world tech - real or theorised that'll get us to another star in a meaningful timeframe.

I know people might talk about fusion engines or anti-matter drives but they suffer from the same energy problems as the solar sail (i.e. massive energy requirements and nuclear levels of excess heat).

Similarly, I know a lot of people are suggesting a higher time warp setting, but I maintain that a Space Program mature enough to build an intersteller ship, even one that only manages 1% the speed of light, can't simply be parked for decades for the sake of that one mission. I also maintain that any sublight drive capable of this kind of speed just breaks the in-system side of the game.

[Person012345]

1. KSP is not a simulator it's a game.

2. I don't think people understand just how long interstellar travel takes, especially if you want to go anywhere further than the nearest star. Granted distance will be scaled down, but still.

3. Since afaik new star systems are not confirmed (they're in the do not ask list because they've been suggested, they've been heard and are being considered as a possibility), I don't think this is an issue yet. I'm not really sure it's worth talking about at this point.

[AngelLestat]

MRab2:

This will be fun.

You want to send 1000 tons to another star? You cant send even 1000 tons to the moon XD

And why you need to send all your stuff in one trip? This is beamed sail, what is mean that one time that you have all set up. You can use it to send anything you want how many times you want, and you can scale up the laser power wherever you want.

And 1000 tons??? If you would build a interstellar ship, you need to use the best materials that you can find, becoz each kg count by a lot.

Graphene and carbon nanotubes are very close to reach big scale production. We are using that in tennis racquets right now.

Graphene is 200 times more lighter than steel to the same strength, but lets say that we use low quality graphene, only 30 times more light.

The first step is not send the titanic to there.. of course you will start with a small probe like everybody else. Or your first mission to jool was 500 tons?

For example if you see the weight estimation for the venture star (avatar) is 350 tons. And is a cargo ship!

And the power of 1TW that i mention was to get 1g, you dont need 1G! you can do it with 0,3g and it will be also great.

Like I said, the first step can be send a mirror that can be use it like telescope, telecomunication and like focus lens, it needs to be in the focus point from kerbol and the star that you want to visit.

So you can use the kerbol sun like a giant telescope using the gravity like lens. Then you can learn all you need to know about this star system. You will can see even if the planets had trees or not .

Second step, you build your power colector with roils of graphene.

(I know you talked about placing it between Mercury and the Sun, but that would be silly – radiation would make servicing them difficult) solar energy is around 1.3kj per square metre.

Why? you need to send people?

And you are concern about servicing in KSP?? when some post back you was talking about FTL? hahaha

In that distance the power that you get by m2 is 20000w, here in earth is 1300w.. so there is a little of difference.

Also you will need a radiator of the same material with a rankine cycle to improve efficiency.

Then you mount the laser in the same spot and you pointed to the mirror in the focus spot, this mirror needs to be on an asteroid, so you can burn a little of mass of the asteroid to compesate the laser thrust.

The sail can be made with 2 stage to brake, or 3 stage to come back.

By comparison, warping space might be a walk in the park.

The tests being carried out on the Alcubierre drive are testing the maths, and the maths suggest the power requirements are much, MUCH lower than the numbers talked about above.

Why you dont read the wikipedia about alcubierre drive, that is the basic step to start talking about that..

Uh, no. The proposed Alcubierre drive does NOT break physics. We know space can expand and contract and we know it's not limited to the speed of light and the reason there's a big hoo-hah about it at the moment is because the maths being tested suggest realistic energy levels are required. Far more realistic than the solar sail model above.

How I said... read... and then read more. To bend space, you need energy, the rules of the thermo dinamics are the strongest rules from all.. They always are right.

Edited August 7, 2013 by AngelLestat

[Skorpion]

It is still very much in the realm of theory

It's your semantics I have a problem with. I agree it's in the realm of theory. That's not the same thing as being in the realm of fantasy.

And "handwavium" means "I'm feeding you goobledeegook that I don't want you to think to heavily about", which is the exact opposite of "we have mathematical models suggesting this is possible, but we need to think about them more". Your use of "unobtanium" is more forgivable, because the Alcubierre drive requires negative energy, which is problematic. However, negative energy must exist because our universe is still expanding, and we know that quantum fluctuations can create a net negative energy.

All I'm saying is that the Alcubierre drive shouldn't be lumped together with stargates and dilithium crystals.

But I think the simplest solution in gameplay terms is just to let you click on your trajectory and choose "fast forward to here". That way, even if your destination is a thousand years in the future, you don't have to wait for it. However, it does assume that Kerbals are immortal. (At least, as far as age is concerned; they can clearly still die in rocket disasters. Maybe that's why they're so eager to throw caution to the wind!)

[Scoundrel]

It's your semantics I have a problem with. I agree it's in the realm of theory. That's not the same thing as being in the realm of fantasy.

It is and it isn't, but I see I've ruffled some feathers so I'll simply state that my position is: if it requires me to "pretend" that the propulsion system can be built because there is currently absolutely no way to physically build it, then, to me, it exists only in the realm of fantasy, no matter how good the theory, because plausibility does not equal possible reality (this is where we go into credibility, which is a completely different playground when it comes to speculative science fiction).

This is why I consider (at this time) the Alcubierre drive in the same realm as a Higg's drive, which is an equally plausible drive, yet also pretty much in the realm of fantasy because the amount of time it will take just to confirm if they're a credible means of propulsion by itself is so speculative that it could be centuries before we know whether or not either are actually doable.

If this attitude still offends you, then I apologize and I blame it all on Clarke, Asimov and Heinlein.

And "handwavium" means "I'm feeding you goobledeegook that I don't want you to think to heavily about",

Actually in SF that's called Technobabble, where as Handwavium is "Ignore the man behind the curtain" style of physics,. In order for the Alcubierre drive to function, we have to engage in handwavium because we still don't know exactly how exactly it will be propelled, plus there's those issues that pop up such as: surviving within the bubble; causality issues; mass-energy requirements; radiation; etc. that we have to ignore in order for it to work.

which is the exact opposite of "we have mathematical models suggesting this is possible, but we need to think about them more".

That's actually what Unobtanium is (quoting from Atomic Rockets) "We can't build a physical example of it, but insofar as we can postulate that it can be built at all, the laws of physics say it would behave like thus and so." If we tried to design a vessel with an Alcubierre drive, the technical drawings would consist of detailed deck plans as well as life support and habitation/power systems and so forth, but the drive would consist of an empty box marked "Alcubierre drive" with a big fat question mark, and a link to a wikipedia page saying "this is how it would work if it existed." In comparison, the VASIMR would have pretty detailed drawings, as would Daedelus drives and other near future propulsion systems, and they would even have reasonably accurate calculations as to what their parameters are.

Your use of "unobtanium" is more forgivable, because the Alcubierre drive requires negative energy, which is problematic. However, negative energy must exist because our universe is still expanding, and we know that quantum fluctuations can create a net negative energy.

Actually this is just more handwavium/unobtainium as opposed to macguffinite (which is sort of what you're hinting at, as macguffinite is something that is made up for the technology to function, which isn't applicable here since we don't have to imagine up a magical fuel for the Alcubierre drive to function).

All I'm saying is that the Alcubierre drive shouldn't be lumped together with stargates and dilithium crystals.

That wasn't ever my intent, but I can understand your distress at my semantics regarding speculative propulsion systems, so for that I apologize. As a hard SF fan it wouldn't have occurred to me to lump speculative science - even though I posited the concept as fantasy - with actual science fantasy... or that anyone else would, which is where I feel the friction is coming from.

Anyhow, I'm enjoying the lively debate!

[MRab2]

MRab2:

This will be fun.

I'm, glad you're enjoying yourself. I am too.

You want to send 1000 tons to another star? You cant send even 1000 tons to the moon XD

You want a two-decade manned mission to travel 9 light years (round trip) in less? As I mentioned this is only twice the mass of the ISS an it only has to sustain a crew of about 5 for a few months at a time - has no propulsion system, no centrifuge (which you WOULD need for a mission that long, no high powered communication system, no hydroponics, minimal radiation shielding compared to what you'd need for long term deep space, and no MASSIVE heat exchange system (which I personally think is the key element you're missing.)

And why you need to send all your stuff in one trip?

Because that makes more sense.

This is beamed sail, what is mean that one time that you have all set up. You can use it to send anything you want how many times you want, and you can scale up the laser power wherever you want.

Yes, but can only power one ship at a time. If you've got to spend 18 months accelerating a ship then the follow on mission will be 18 months behind it.

And 1000 tons??? If you would build a interstellar ship, you need to use the best materials that you can find, becoz each kg count by a lot.

No? Really? Believe it or not I took that into account. I still think 1000 tonnes is low for this size of mission.

Graphene and carbon nanotubes are very close to reach big scale production. We are using that in tennis racquets right now.

Graphene is 200 times more lighter than steel to the same strength, but lets say that we use low quality graphene, only 30 times more light.

Yup, still feeling I'm in the ballpark. I notice you're not giving an estimate.

The first step is not send the titanic to there.. of course you will start with a small probe like everybody else. Or your first mission to jool was 500 tons?

So what? Manned missions are all that count.

For example if you see the weight estimation for the venture star (avatar) is 350 tons. And is a cargo ship!

It's also entirely fictional. Not really the best basis for comparison. Also, the weight estimate does NOT come from the same people who made the movie iirc.

And the power of 1TW that i mention was to get 1g, you dont need 1G! you can do it with 0,3g and it will be also great.

Ok, let's take that. 6.7 newtons per Gw. For 0.3g that would be a spacecraft with a mass of 2.2 tonnes. Which is less than my last car weighed. Not talking probes here. I'm talking manned missions. The Apollo capsule and lander were 45 tonnes - and that was 3 men popping out across the road for a few days.

Like I said, the first step can be send a mirror that can be use it like telescope, telecomunication and like focus lens, it needs to be in the focus point from kerbol and the star that you want to visit.

So you can use the kerbol sun like a giant telescope using the gravity like lens. Then you can learn all you need to know about this star system. You will can see even if the planets had trees or not .

Don't care about the unmanned portion of the mission, but we'll go with it - it's equally impractical.

Why? you need to send people?

Are all your Kerbal mission unmanned? Why not?

And you are concern about servicing in KSP?? when some post back you was talking about FTL? hahaha

Remember, the core of this discussion was your claim that within 50 years we'd have the technology to send a mission to Alpha Centuri that would take only 7 years. Wobbling between real world and Kerbal is only going to confuse matters. For clarity - everything I'm talking about is real world and NOT game mechanics. We can talk about game mechanics after you understand the physics

In that distance the power that you get by m2 is 20000w, here in earth is 1300w.. so there is a little of difference.

Placing you installation that close to the sun might seem like a good idea – all that lovely energy means your collectors don’t have to be that big, but it’s a disaster waiting to happen. As you mentioned – 20kw/m2 (I don’t know if that’s accurate but I’ll accept it for now) is an engineering nightmare. Every surface exposed to that will need to be cooled, and cooled A LOT. If the cooling system fails for whatever reason, even for a short period of time, your whole installation is essentially doomed. That close to the sun you’re not going to be sending people out, so this is a completely automated facility – including the repair systems. So if something happens that it wasn’t programmed for then DOOM!!

That’s a huge gamble that no one’s going to sign off on, and all this is before you even consider the logistics. Even if you break the whole thing down into 100 10gigawatt facilities – you’re going to need to assemble them in Earth orbit and fly them to low steller orbit. A ship that can accommodate a 10 gigawatt laser and energy collector and cooling system is going to be BIG and I mean REALLY big. Even assuming your photovoltaics are hand-wavingly efficient at 90%, and your laser is similarly stupidly efficient you’ve still got 2 gigawatts of heat to deal with which you can only shed using radiators.

Now, I spent a few years working in a nuclear power station. It was an advanced gas-cooled model with two reactors. Total power output: 1.2Gw and I know exactly how big the cooling system was. It was f**king huge (by spaceship standards) and had (iirc) 100 tonnes of CO2 running through it. All this CO2 is going to have to be fed into enormous radiators to very inefficiently bleed the excess heat off into space.

And all of this mounted on a ship that can move it from Earth orbit to low solar orbit – and you have to build 100 of these!!

Out at Earth orbit where the power density coming from the sun is MUCH more manageable you can build MUCH smaller ships with much bigger solar collectors and just toss them out with enough oomph to escape Earth’s gravity. In all likelihood some compromise around Venus’s orbit would be the answer.

Now, we come to the OTHER end of the equation. 1 TW of radiant energy from your laser array striking your sail ship. A 1 terawatt coherent beam of energy would, in any other context, be considered a weapon of mass destruction. Seriously, you could level cities with this kind of power and you’re firing at one little 2 tonne ship. Even if the ship could convert 99% of the incoming energy to kinetic energy that still leaves 10gigawatts of heat that it has to cope with. Since I was being silly with 1000 tonnes (?!?) perhaps you can tell me how within 50 years one small ship is going to be able to manage to shed 10gigawatts of heat without access to a large body of water (which is how we do it now).

To put this into perspective, this is enough energy to turn 24,000 litres of water to steam every single second.

The bottom line is this – this technology is only any use for sending small payloads out of the system at very low acceleration. Otherwise the energy requirements start jumping through the roof and the engineering and resources required rise exponentially. Any talk of sending crewed missions to neighbouring star systems is *almost* as much science fantasy as the Alcubierre drive.

Also you will need a radiator of the same material with a rankine cycle to improve efficiency.

This is going to be one fricking HUGE radiator. I'm considering crunching the numbers just for a laugh.

Then you mount the laser in the same spot and you pointed to the mirror in the focus spot, this mirror needs to be on an asteroid, so you can burn a little of mass of the asteroid to compesate the laser thrust.

I see. Is the area of space between the sun and Mercury littered with handy asteroid? No. So we're towing asteroid(s) in to position as well now? Actually, what am I thinking? WTF do you need an asteroid for? Wouldn't the kinetic energy from the outgoing beam be balanced by the energy coming from the sun?

Why you dont read the wikipedia about alcubierre drive, that is the basic step to start talking about that..

There are more sources than Wikipedia.

How I said... read... and then read more. To bend space, you need energy, the rules of the thermo dinamics are the strongest rules from all.. They always are right.

Trust me dude, I'm the one teaching you here. Take the above example - the laws of thermodynamics have NOTHING to say about bending space. Let's see, from memory 1st Law - energy is always conserved 2nd Law - Equilibrium is the norm and 3rd Law is Entropy always increases.

Think about it for a second. Large masses distort space. Yes? That is afterall what gravity is. How much energy do they expend doing it?

[AngelLestat]

The explanation that made Scoundrel to Scorpion was almost the same as I would done the last post to Mrab2 if I had the time. But I want to add something:

However, negative energy must exist because our universe is still expanding

This is like said GOD must exist because there is an universe. WE DONT KNOW!

Is just an hypothesis, maybe there is not such thing like negative energy, maybe there are other universes who are interfering in some way with ours, or it can be other thing, we dont know!

Trying to travel FTL before being able to reach the half of C is like trying to solve Fermat's Last Theorem before learn how to add.

I read a lot of articles and studies about ways to avoid the light speed limit in macroscopic scale or in the quantum world, and every single method finds always a weird effect that prevents this to happen.

The conclusion always is "nothing can travel faster than light" And it has something to do with the information and the real shape of the universe.

I believe that the question about why the speed of light is how it is, inclose the bigger mistery of our universe.

And jump our biggest limit and mistery just becoz we were start trek fans or we dont have the courage to face it; is silly, is like win a game without play it.

You want a two-decade manned mission to travel 9 light years (round trip) in less? As I mentioned this is only twice the mass of the ISS an it only has to sustain a crew of about 5 for a few months at a time - has no propulsion system, no centrifuge (which you WOULD need for a mission that long, no high powered communication system, no hydroponics, minimal radiation shielding compared to what you'd need for long term deep space, and no MASSIVE heat exchange system (which I personally think is the key element you're missing.)

But try to understand because is not so easy for me to write in English.

First you keep mention ISS, but this is not a space station, and the materials that now we use can be 50 times better.

Centrifuge?? why for? you can have a constant acceleration of 0,3g.. or if the technology aloud it some kind of hibernation so you dont need food or water (a lot less weight), why not? bears and thousands of other animals do it.

Massive heat exchange?? WHAT?? You dont need, the same sail is the radiator, and it reflex the 99% or more.

High power comunication? again.. Sail! The 10km2 concave shape is perfect for this. And it use laser instead radio, and the sun gravity works to focus in the same way that focus the laser beam.

And against radiation you only need to protect the crew, no the sail. A superconductor wire will help a lot like shield. And you dont need power for that.

Because that makes more sense.

Yes, but can only power one ship at a time. If you've got to spend 18 months accelerating a ship then the follow on mission will be 18 months behind it.

Sense?? for who? You can send all the stuff that the crew will need before them arrive, and the first probes will improve all the info that you need for the mission.

And how I said, you start from a small collector and a laser and you will scale up from there. And that takes time.

How many time pass between each mission to mars? or saturn?

But no! you want to send missions with less time frame that we do to our neighboring planets.

Yup, still feeling I'm in the ballpark. I notice you're not giving an estimate.

1 km2 of carbon nanotube weights 38 kg, The carbon nanotubes are made in a specific distance to reflect a specific laser frequency, a piece of this sail (hand side) was already made in laboratory.

Graphene is 4 times more lighter than carbon nanotubes. But even if we take an average weight 30 times more lighter than ISS, you will have that you can send some crew in himbernation with only 5 or 10 tons.

Other requirements can be send before and after.

It's also entirely fictional. Not really the best basis for comparison. Also, the weight estimate does NOT come from the same people who made the movie iirc.

Is the same people! James cameron 1 year before the movie ask to peregrinno and other folks to design a real interstellar ship for the movie 1 year before. The ship takes into account many studies and update these ones.

Of course all the details are omitted in the movie just as the pandora, but all have scientific support.

The ISV is the most real design from an interstellar ship shown in a film. Even the size of the radiators match their true requirements.

I made the math.

The Apollo capsule and lander were 45 tonnes

Can you give me a source of that? I cant find it.

It all places said 10 tons with the fuel. And you need to count that each 1 kbytes of memory in that time weight like 10 kg. Just to have in mind.

Are all your Kerbal mission unmanned? Why not?

In fact.. mostly.. yeah. And all the real missions are unmanned!

Remember, the core of this discussion was your claim that within 50 years we'd have the technology to send a mission to Alpha Centuri that would take only 7 years. Wobbling between real world and Kerbal is only going to confuse matters. For clarity - everything I'm talking about is real world and NOT game mechanics.

50 years with all the budget into that. Yes. I claim that. And it start with a unmanned probe.

We can talk about game mechanics after you understand the physics

Really? an insult? haha.. Are you sure about your claim.. becoz it seems that you dont

But I'll be glad when you convince me about FTL drives with the same technical details, I am waiting for...

Maybe your connection will be off before that happens..

As you mentioned – 20kw/m2 is an engineering nightmare

Why is that? A smoothing iron release 1500 watts. And 20kw/m2 is equal to 400w in the same smoothing iron area.

And Graphene melting point is 5500 K at vaccum.

Every surface exposed to that will need to be cooled, and cooled A LOT. If the cooling system fails for whatever reason, even for a short period of time, your whole installation is essentially doomed.

You find the drastic side to all

Even without cooling system and absorbing 20kw in heat, the graphene it would be ok. Higher the temperature it is, more fast radiates.

But you are forgeting something.. "Efficiency", They reach in laboratory with graphene 70% of effiency, This is absobing light and infrared light (also heat), So from those 20kw/m2, You only need to dissipate 6kw/m2. And the rankine circle is to improve the Efficiency, and you only need a small surface to do that.

you’re going to need to assemble them in Earth orbit and fly them to low steller orbit. A ship that can accommodate a 10 gigawatt laser and energy collector and cooling system is going to be BIG and I mean REALLY big. Even assuming your photovoltaics are hand-wavingly efficient at 90%, and your laser is similarly stupidly efficient you’ve still got 2 gigawatts of heat to deal with which you can only shed using radiators.

How I said, Graphene can be folded and is very thin, You can send roll pairs of 10x500m and attach them into a spinning collector that will keep deploy by centrifugal force.

Meanwhile you can sell the power to the earth to fund and complete the collector.

Now, I spent a few years working in a nuclear power station. It was an advanced gas-cooled model with two reactors. Total power output: 1.2Gw and I know exactly how big the cooling system was. It was f**king huge (by spaceship standards) and had (iirc) 100 tonnes of CO2 running through it. All this CO2 is going to have to be fed into enormous radiators to very inefficiently bleed the excess heat off into space.

I already answer that. But if you want, like homework. You can calculate using Stefan-Boltzmann equation.

Taking the example of avatar ISV, the 2 radiators 150x400m can release 24 TW with a working temperature of 4500K.

1 TW of radiant energy from your laser array striking your sail ship. A 1 terawatt coherent beam of energy would, in any other context, be considered a weapon of mass destruction. Seriously, you could level cities with this kind of power and you’re firing at one little 2 tonne ship. Even if the ship could convert 99% of the incoming energy to kinetic energy that still leaves 10gigawatts of heat that it has to cope with. Since I was being silly with 1000 tonnes (?!?) perhaps you can tell me how within 50 years one small ship is going to be able to manage to shed 10gigawatts of heat without access to a large body of water (which is how we do it now).

First: Any interstellar drive can be considered a weapon of mass destruction. But the beamed sail is the the safest method in that aspect.

If you use Antimatter for example, you need to carry all that energy from the first moment. Instead the beamed sail produce the energy for each second of the trip.

Also maybe you can place the laser behind the sun (lagrange 3). Or in jupiter (in this case you need to collect the energy using its magnetic field, but you cant use jupiter gravity to focus the laser, in that case you will need many frensnel lens that can be drop it by the first probe going there.

The sail is not a problem, in fact, the sail are big to compesate the accuracy problem (is the most difficult to achieve, but is just a technical problem), If you divide the power into the sail area less the 99% you will get that there are not heat problems.

The bottom line is this – this technology is only any use for sending small payloads out of the system at very low acceleration. Otherwise the energy requirements start jumping through the roof and the engineering and resources required rise exponentially. Any talk of sending crewed missions to neighbouring star systems is *almost* as much science fantasy as the Alcubierre drive.

Taking how much energy you will need to do antimatter or the low delta v with fussion, etc.. Beamed sail is far the best option, And you will find the same opinion in almost all interstellar science sites.

Is the only feasible option by the moment. And the energy requirements and technology are unimaginably lower than "the fantasy" Alcubierre drive.

is even embarrassing you've courage to compare about payloads.

There are more sources than Wikipedia.

Yes, you always can find that in tabloid magazines aside the horoscope section.

Trust me dude, I'm the one teaching you here. Take the above example - the laws of thermodynamics have NOTHING to say about bending space. Let's see, from memory 1st Law - energy is always conserved 2nd Law - Equilibrium is the norm and 3rd Law is Entropy always increases.

Think about it for a second. Large masses distort space. Yes? That is afterall what gravity is. How much energy do they expend doing it?

Thanks, I am very pleased to have you as a teacher

But this smells suspiciously like perpetual motion, and would break the well established principle of conservation of energy. There you go.

And is not the only principle that Alcubierre drive breaks. But is the most important, and nobody mess with the thermodynamics laws.

Edited August 9, 2013 by AngelLestat

[rkman]

James cameron 1 year before the movie ask to peregrinno and other folks to design a real interstellar ship for the movie 1 year before.

That ship is not as real as the word "real" seems to imply.

[Person012345]

The explanation that made Scoundrel to Scorpion was almost the same as I would done the last post to Mrab2 if I had the time. But I want to add something:

This is like said GOD must exist because there is an universe. WE DONT KNOW!

Is just an hypothesis, maybe there is not such thing like negative energy, maybe there are other universes who are interfering in some way with ours, or it can be other thing, we dont know!

We think that there must be some form of "negative energy" because we measured the curvature of the universe it came out to 0 as far as we can tell (and this would require a total mass-energy of 0). Dark energy which is the cause of the expansion of the universe (and we have no idea what it is, it's not so much "theoretical" as "a word for something that we don't know what it is") isn't widely regarded to have negative energy afaik. In that context gravity has negative energy and cancels out the energy of everything else.

Or something

Edit: Although I think the negative energy plays a part in allowing expansion in a flat universe, it's not as simple as "it's causing it" (obviously, since gravity does the opposite). And it requires the assumption that it is flat. Which it looks like it may well be.

Edited August 9, 2013 by Person012345

[Person012345]

By the way, when talking about this stuff it's a good idea to bear in mind that reality makes absolutely no sense whatsoever.

[AngelLestat]

That ship is not as real as the word "real" seems to imply.

I said that is the most real design for an interstellar ship that was used in a movie. So I dont understand your reply.

But if you said that is all no senses. Tell me with more detail what is wrong about the Venture Star.

By the way, when talking about this stuff it's a good idea to bear in mind that reality makes absolutely no sense whatsoever.

Something seems like no sense when we do not understand it. And how we are the ones who defines what is real or not depending our limited evidence, it will be always a lot of things without sense.

We think that there must be some form of "negative energy" because we measured the curvature of the universe it came out to 0 as far as we can tell (and this would require a total mass-energy of 0). Dark energy which is the cause of the expansion of the universe (and we have no idea what it is, it's not so much "theoretical" as "a word for something that we don't know what it is") isn't widely regarded to have negative energy afaik. In that context gravity has negative energy and cancels out the energy of everything else.

Or something

Edit: Although I think the negative energy plays a part in allowing expansion in a flat universe, it's not as simple as "it's causing it" (obviously, since gravity does the opposite). And it requires the assumption that it is flat. Which it looks like it may well be.

We dont know that... is just an hipothesis.

The only thing that we know is that einsten equations cant explain the movements of matter that we see with telescopes at super macro scale.

There is only one evidence who can have different explanations.

1- Einstein law of gravity need some corrections.

2- Other universes.

3- dark matter theory that it does not said nothing in particular about what is "dark matter".

4- Something about the structure about our universe that increase the effect on matter.

5- thoudsen of other posibilities that we dont know or we cant imagine yet.

Even the standard model of physsics has nothing to said about dark matter.. Not even a clue. And that model is almost complete.

You can said that something exist when is prove it with evidence and model predictions.

For example now we can said with a 99.9999999999999% that the higs boson exist becoz was prove it with that chance. Becoz we saw it and we measured it and all has sense with our mathematical models and predictions.

And even if dark matter exist, we dont know if we can interact with it, or use it.. Or how difficult it will be.. We dont know NOTHING.

There are other mathematical models who does not need the existence of dark matter or dark energy to explain the movement of galaxies or clusters. (no yet galaxy clusters)

But not take my word, maybe Michio Kaku can explain that better.

http://www.dnatube.com/video/28282/Michio-Kaku-on-Dark-Matter-and-Parallel-Universes

Edited August 10, 2013 by AngelLestat

[MRab2]

Stuff

Yes, I keep mentioning the ISS – it’s the biggest Real World object we’ve put into space. Just because it’s a space station doesn’t mean it’s an invalid basis. What do you imagine the difference between a spacecraft and space-station are? Do you imagine space-stations are somehow inherently heavier than spacecraft? Some of the proposed spacecraft for moving people around within the solar system are considerably heavier.

And “grapheme†isn’t a catch-all solution. Yes, it’s a very good material with some extremely interesting properties and a LOT of material but it doesn’t solve everything.

*

As for the venture Star weighing 350 tonnes. Firstly, this is b*****ks and secondly, I can’t find any source for this. The figure is conspicuously absent from the Avatar wiki. Thirdly, whilst Cameron may have consulted some people in the know regarding the design you’ve no idea how much creative license he took with their suggestion. Fourthly, it’s 22nd century technology. In conclusion its value as a basis for considering weight is virtually zero.

*

I do owe you an apology though – I said I was trying to get you to understand the physics. I really meant the engineering, which is an altogether different kettle of fish and my back yard. You asked why I always look for the drastic side of things – it’s pretty much my job; to identify the high risk elements of a design and find viable solutions.

*

So, to distil this discussion down here’s the bottom line – whilst a beam sail interstellar ship is technically viable it's not going to happen within your 50 year timeframe. To get even a small probe up to relativistic velocities would require incredible resources and numerous technologies that just aren’t even close to being realised. Not to mention a fairly mature space infrastructure including asteroid mining and orbital factories. Even a 10gigawatt laser platform would be a huge vessel by today’s standards – several thousand tonnes of hardware at least, maybe 10s of thousands (you’re talking about a machine that will channel enough energy to power Iceland).

And to hit your target you need AT LEAST 10 of them in orbit – probably more, lasers are only around 10% efficient at the moment. I don't see them being 90% within the next 50 years, even with high temperature superconductors (which even in 2063 will still need to be kept cold).

You asked why, if you moved it close to the sun I thought it needed cooling when the sunlight falling on it only had a third the energy of a domestic iron. Consider the following -

Irons have thermal cutouts to prevent them from overheating and Mercury's surface temperature is 800K – you imagine solar cells are going to be able to handle that kind of abuse without cooling? The Solar Probe Plus planned for 2018 will only use uncoolled solar panels when it's beyond around 40 million km. the point being - it's easier to build a bigger collector (which we'll assume is graphene with solar cells printed onto its surface) than a smaller one that needs cooling. But the elephant in the room is still the laser itself.

Finally, apologies for the delay in answering – real life got in the way.

[MRab2]

I said that is the most real design for an interstellar ship that was used in a movie. So I dont understand your reply.

But if you said that is all no senses. Tell me with more detail what is wrong about the Venture Star.

No official mass for it (you'll need to provide a link), radiators are WAY too small and the shuttles look like the freaking space shuttle!

[DJEN]

The term "FTL" is inaccurate, "LBB"(Light Barrier Bypassing) is more accurate.

Like your idea though.

[DJEN]

Also, this thread is developing into a war zone.

THIS THREAD SEEMS TO REQUIRE IMMEDIATE LOCKING.

[AngelLestat]

MRab2

Yes, I keep mentioning the ISS – it’s the biggest Real World object we’ve put into space. Just because it’s a space station doesn’t mean it’s an invalid basis. What do you imagine the difference between a spacecraft and space-station are? Do you imagine space-stations are somehow inherently heavier than spacecraft? Some of the proposed spacecraft for moving people around within the solar system are considerably heavier.

Hi Mrab2, Very glad to see your response.

I already told you the differences. First the new materials properties and weight that are coming. Second, if you allow the hibernation option, then your volume decrease a LOT. Also in the ISS there is not inflate modules. I already show that you can use the sail like radiator and antenna or the acceleration like artificial gravity. The sail will help you to maneuver in the new star system. In that time some little shuttle like skylon can help you a lot. Or maybe 1 micro gram of antimatter to be the catalyst of a fussion engine to be able to take off from some planet surface back to the sailship. And it can be easy mining an asteroid to get hidrogen from water.

So yes, it can be very different from a ISS, more considering that you not have to send all at once.

And “grapheme†isn’t a catch-all solution. Yes, it’s a very good material with some extremely interesting properties and a LOT of material but it doesn’t solve everything.

Maybe not.. but lets make a list: Super conductor that works at room temperature, the material with higher melting point that we know. best thermal conductor, 200 times more strong than steal, convert electromagnetic waves into electrricity "perfect cell", flexible, transparent, is perfect to combine with other materials, is carbon so is cheap and 100 other great qualities... Seriusly read the other 100.

As for the venture Star weighing 350 tonnes. Firstly, this is b*****ks and secondly, I can’t find any source for this. The figure is conspicuously absent from the Avatar wiki. Thirdly, whilst Cameron may have consulted some people in the know regarding the design you’ve no idea how much creative license he took with their suggestion. Fourthly, it’s 22nd century technology. In conclusion its value as a basis for considering weight is virtually zero.

http://www.pandorapedia.com/human_operations/vehicles/isv_venture_star

It said 350T all the cargo, this include the 2 shuttles.

For example it will be like this in metric tons:

shield 5 + crew 20 + habitation section 30 + both shuttles 60 + cargo 250 + ship structure 20 + engines 10 +? radiators 10 + spheres 5, sail 20.

For habitation section, 200 men/women, average weight 70 kg with an extra 70 kg on structure and cryo for each person.

But we need to take into account that we dont need the 2 shuttles, why carry the 2 shuttles and then go back to the earth with the 2 shuttles?

You can leave 2 in pandora and 2 in earth working with the 12 ISV.

It said that ISV reach 0,7c, this mean that the engine ISP it has to be more than 0,7c by definition.

It uses a magnetic nozzle, so these are some parameters that we can have:

ISP - Total mass - Fuel Mass - Gamma ray used - Heat Release/s - Heat Absorb/s

0,77c / 1000 t / 650 t / 50% / 742 TW / 74 TW

0,95c / 860 t / 510 t / 88% / 139 TW / 14 TW

1.0c / 800 t / 450 t / 100% / 0 / 0

The 2 radiators release 24Tw, and if use the ISV sail like radiator it can release 130 TW of heat.

I really meant the engineering, which is an altogether different kettle of fish and my back yard. You asked why I always look for the drastic side of things – it’s pretty much my job; to identify the high risk elements of a design and find viable solutions.

Great, I am system engineering, I love to see different systems (any kind) and find a way to improve them.

So, to distil this discussion down here’s the bottom line – whilst a beam sail interstellar ship is technically viable it's not going to happen within your 50 year timeframe. To get even a small probe up to relativistic velocities would require incredible resources and numerous technologies that just aren’t even close to being realised. Not to mention a fairly mature space infrastructure including asteroid mining and orbital factories. Even a 10gigawatt laser platform would be a huge vessel by today’s standards – several thousand tonnes of hardware at least, maybe 10s of thousands (you’re talking about a machine that will channel enough energy to power Iceland).

But you're forgetting something crucial that I mentioned. "With all the budget into that!"

Lets see only the USA budget, NASA budget is only 1% of USA military budget... Now add the rest of the world.

Also for the first mission you can use microwave instead laser. Microwave instruments are a lot more cheap than optic instruments.

Is more dificult to get accuracy in long distances, but you can get bigger accelerations.

In this case you dont need payload, all the sensors and instrument can be in the same sail structure, this will be also had a coated paint over the sail mesh,

this gives extra propulsion at begining due to evaporation. A sail like this can reach 0,1c, it accelerate at 100G the first days.

This idea is taken very seriously by NASA to move large payloads within the solar system or for ort cloud missions.

To brake you can have a magsail, is just a superconductor wire, with this you can brake from 0,7c to almost 0 in 2 years without using fuel or energy.

And to hit your target you need AT LEAST 10 of them in orbit – probably more, lasers are only around 10% efficient at the moment. I don't see them being 90% within the next 50 years, even with high temperature superconductors (which even in 2063 will still need to be kept cold).

A laser at vaccum and 3K degrees can reach 30% of effiency with ease. And I am talking about to day normal lasers.

If you add all the advance that we achieve in lasers to day that number can rise a lot, also add all the advances that we are getting in Metamaterials, dielectric, plasmonic, superlens, dichonics and nonoantenas and you will have your dream laser.

The next particle accelerator it will be with lasers instead magnetic fields.. maybe that tells you something.

Irons have thermal cutouts to prevent them from overheating and Mercury's surface temperature is 800K – you imagine solar cells are going to be able to handle that kind of abuse without cooling? The Solar Probe Plus planned for 2018 will only use uncoolled solar panels when it's beyond around 40 million km. the point being - it's easier to build a bigger collector (which we'll assume is graphene with solar cells printed onto its surface) than a smaller one that needs cooling. But the elephant in the room is still the laser itself.

Maybe new Irons come with thermal cutouts, and these are in case you keep the Iron prone. Do the math and you will see how much heat release by radiation and how much heat release by convection, it will be close to 1000W. Or you can put your hand close and compare with another product xd

Mercury is 700K, half between sun and mercury it will be more than twice. Lets round in 2000K, then you need to reduce the 70% from the graphene efficiency, converts almost all the heat into electricity, lets said 700K left, and melting point is 5500K. So again, The rankine circle with extra radiator is just to get more effiency.

And you mention "graphene with solar cells printed onto its surface" graphene is the same cell, it does not need a cell printed.

Edited August 14, 2013 by AngelLestat

[Outlander4]

I don't really understand the purpose of this discussion apart from trying to educate/scream at each other.

My opinion is that KSP shouldn't have any form of FTL propulsion at all because it's not realistic and not fun. Its educative value is zero; anyone can imagine flying around at 100 times c, meeting space babes, seeing places and generally boldly going wherever they want, we have other games for doing just that, and some of them are even free.

Using some form of still-not-existing-but-feasible propulsion like nuclear/thermonuclear pulse drives (Daedalus and so on), uranium salt-water rocket (it has trouble with fuel storage though) or fusion aka z-pinch drive (which requires fusing deuterium in a linear solenoid tube - for God's sake, it's so ridiculous it might even be possible) our Kerbals may achieve a decent fraction of the speed of light (say, 25%. 15%? Even 5% is fine!); combined with a simple timer that tells you when your ship is about to reach some point or the other and game mechanics that excludes interstellar ships from the simulation after, say 'locking trajectory and burn time', we may be able to just build the damn thing, fuel it, ignite the engines, and forget about it doing other things waiting for it to accelerate, decelerate, and reach its destination. So, basically, ship will just 'jump' to the other star system...in the amount of time required to fly to it. And with distances compressed to KSP scale it will take only decades of game-time; my Laythe colonisation effort took me almost 30 years of game time (before my video card burned up and I stopped playing games altogether...damn it)

I think it's a decent solution; it won't stress physics engine with calculations; it will be realistic enough, and huge effort required to build such a ship in orbit and to fuel it will somewhat limit its use, especially in the career mode. We need just some patience and some long-term planning to do it; two qualities we lack the most in real life.

[rkman]

I don't really understand the purpose of this discussion apart from trying to educate/scream at each other.

This discussion is based on the incorrect assumption that the 'FTL drive' that Squad has in mind is a magical-get-you-anywhere-instantly drive.

... basically, ship will just 'jump' to the other star system...in the amount of time required to fly to it.

Maybe Squad does have a good reason for wanting to move the ship physically between the stars, maybe they want the player to be able to interact with a ship that's on an interstellar trip. But other than that the method you describe seems to make perfect sense.

[Outlander4]

Maybe Squad does have a good reason for wanting to move the ship physically between the stars, maybe they want the player to be able to interact with a ship that's on an interstellar trip. But other than that the method you describe seems to make perfect sense.

Yeah, I'd be glad to have ship management in interstellar space myself. Things like repairs, moving crew around, course corrections...and it's actually possible to do as well, it's just that we should have different simulations for solar system and for interstellar space...correct me if I am wrong but right now Kerbol (or Sun, if you're pro-NovaSilisko) is the centre of the Universe with everything rotating around it or escaping it into the void.

With another stars there should be another set of simulation - stars themselves orbit the centre of the galaxy, and so would your ship once it's left Kerbol SOI...simulating such things (and at ridiculous speeds at which stars orbit the Galaxy centre...also, add simulating planets' movements for all star systems out there) is going to choke down any PC...

[Morrigi]

For those saying FTL travel is unrealistic, you are simply incorrect. There are already two real-world theories showing that it is possible - wormholes and the Alcubierre drive. Both, given sufficient technological development, may take us to the stars.

And if you haven't noticed, this is not a game focused entirely on realism. Your astronauts are little green men.

[pyro42]

Like Fifi, I'm against warp drive.

The hibernation or cryopreservation (say it as you want) is, for me, a good idea.

It could also be very usefull to have an "auto-traveler" a little tool who could automaticaly fly a spaceship to another planet that you already discovered.

The idea is that you keep the fun : You don't have to make the same travel of two hours ten times, you could manage 5 flights at the same time and it could be used with "routines". By example : to re-fuel a station automatically.

So, when you want to send some crew to a station, around another planet, you just have to plan a travel with your auto-traveler and to time warp.

And of cours, ti would'n make your computer lagging, because all of thoses "travels" would be pre-calculated (except if you want to blow up the vessel who is using the auto-traveler)

[ouion]

My old thread from a year ago.I remember those 0.16 days.

[Scoundrel]

For those saying FTL travel is unrealistic, you are simply incorrect. There are already two real-world theories showing that it is possible - wormholes and the Alcubierre drive. Both, given sufficient technological development, may take us to the stars.

You forgot the Higgs drive - which makes it three real-world theories... and all of them are pure speculation (if I am incorrect, I'd love to see the blueprints for the functioning engine or engines).

As has been suggested before, a scaled down galaxy and drives permitting the player to achieve just 10% of lightspeed would allow journeys to take place in the same amount of time it takes to set up a Duna window and actually travel there; or travel to Jool/Laythe. No conjectural space-warping engine required. In fact, it would take just 6 years for a ship accelerating to 7% of light speed, coasting for 80% of the time, and decelerating once within the system SOI, to travel 0.4LY. If the stars were even closer than that, say 0.1LY, the time would be reduced to under 2 years, all of which are perfectly reasonable timeframes for KSP to function within. It's only when we want stars to be ridiculous distances apart that we start to have real issues with interstellar travel. With x1,000,000 time warp a 6 year journey would only take about 3 minutes realtime to traverse the distance.

That said, the problem with the above solution is that the accel and capture burns would take months real time even at x4 warp. I suspect that the solution would be to make interstellar journeys a function within mission control. Rather than a cutscene or FTL travel via Warp Engines/Stargates/Wormholes/Plotholes, the player would select a Kerbal mission control guy, click "make ship go fastest!" and we get a dialogue box saying "It will take 4.1 years to get to XYZ. Continue? Y/N?" and if we say yes, we find our ship is no longer selectable in map view and we see a transit line that shows the position of the ship and other transit info - it's actually on rails - until it arrives in the next system after it's fake "capture burn". In the meantime, we will be able to either continue to mess around doing other stuff while the ship is in transit, or we can just go "meh" and timewarp until the ship arrives.

The actual science behind all of it doesn't have to be exact or "realistic" or even micromanaged - it just has to provide a gameplay mechanism that allows the player to send ships to other star systems that operate within reasonable realtime timeframes regardless of whichever cognitive rationalization the devs end up going with.