MRab2

They are very different things and technology predates science by several tens of thousands of years.

My vision is simple - I want to explore and colonize dozens of start systems, not just the next one over. All you sub-lighters seem to forget about everything except the system right on Kerbol's doorstep. What about the one after that, or the one after that? When journey times start to creep into decades (as they quickly will a few systems out) it'll start to become pointless to go further. AND SLT means intersteller travel is largely pointless anyway, apart from a pure science point of view. Now, FTL opens up two things, the possibility of ferrying stuff back from the new system and an whole new tech tree of bigger, more powerful FTL engines. My vision is an economy that ultimately runs on anti-matter. A resource that's very difficult to obtain in large quantities. I'm think huge anti-matter collectors orbiting over gas giants, but even then, the quantities harvested not being enough to fuel an increasingly space faring civilization and so the hunt for more gas giants pushes our brave Kerbals further and further out into the larger universe. Game balance. “There is not the slightest indication that nuclear energy will ever be obtainable. It would mean that the atom would have to be shattered at will.† Albert Einstein, 1932 This was 10 years before the world's first atomic pile was built. You'd be amazed at the things we take for granted today that were considered impossible not too terribly long ago... Here's another one. “Space travel is bunk.† Sir Harold Spencer Jones, Astronomer Royal of the UK, 1957 (two weeks later Sputnik orbited the Earth). Of course people think engineering is easy, generally people who don't actually do any engineering. Speaking as an engineer, funding research into FTL looks an awful lot easier than building a half million tonne nuclear pulse rocket. Just because something is theoretically possible to put together something using existing technology doesn't mean it's *actually* possible. Sounds like someone wants to have their cake and eat it. Relaxed/hard physics hmmm?

Only if Squad are stupid, and I personally think they've done a good job so far of proving they're NOT stupid. You imagine the same requirement couldn't be built in to an FTL system? Who says it'll run on batteried? No, it's about breaking the in-system game. Actually no, magic happens here as well. It's tempting to think that relativistic velocities are just a matter of engineering, but harnessing and channeling the energies needed (if using something like an anti-matter drive) means materials with magical properties i.e. ultra high temperature superconductors. Whilst I disagree with him on many things AngelLestast is right in that a beam sail is probably the most realistic sublight model. Intersteller nuclear pulse ships are colossal, starting at around 500,000 tonnes. Since this will need to be scaled down for Kerbal any representation of this within Kerbal will be magical. Then here's an idea - don't build the damn thing. Hell, don't even research it. Stick to the hard physics. Accept journey times in the many decades to centuries as THAT is the most realistic option based on modern physics. I would tend to agree, whilst moving around in space with increasing ease is ultimately the aim of a space program a ship with the thousands of km/s of dV needed to reach another system will reduce interplanetary journeys to a matter of triviality. Whereas with an FTL system the in-system game can be preserved. Yes it'll be easier than it is now - bigger, cooler ships, less fuel constraints but still more involved than "point and accelerate".

Sorry i misunderstood. Please see Sean's reply. It is essentially what i would have said if i hadn't been having a blonde moment.

No you won't. Sorry but your answer is based solely on ONE idea of how an ftl system would work. There is no reason to presume it would work how you are imagining it.

A 1 kilometre diameter asteroid would weigh in at several dozen MILLION tonnes. The NEO Apophis, which caused some concern a while back is 600m long and roughly half that wide and it's weight estimate is around 26 million tonnes. Good luck trying to move that! I suspect asteroids will be on rails.

Because it's one of the most trivial of question and the answer is; it's not terribly important. At the power levels we're talking about you're going to have more than one station and you're not going to base your calculations on them all running 100% of the time, so even if they pass behind the star it doesn't matter. And the task jumps three orders of magnitude on the difficulty scale - now you're talking about pushing asteroids around the system?!? Just to stress the point - I'm not saying its not doable, but representing the task within the context of Kerbal will be completely unrealistic - which I'm FINE with. It's a game, as long as it looks roughly realistic then it's OK. But if you're willing to accept that compromise then claiming FTL shouldn't be in the game because that's not realist starts to look like silliness.

There's a video on Youtube in 0.17 (I think) where they got a ship up to 1.7 X the speed of light. With a *shrunken* universe this would be fast enough.

Don't you mean *magical* hibernation? No they won't. . No, it's still a huge problem. Drivel. In the 50 years since the laser was invented the closest analogue to what's being talked about here puts out about 100kw and it's "continuous" cycle is measured in minutes. You think we'll a laser that's 5 orders of magnitude more powerful and run for months at a time?!? And that laser will almost be every bit as magical as the warp drive you're so against. And neither do you, or anyone else. Our understanding of physics is still developing. We're more likely to have a working theory for FTL in the next 50 years than to have the in-space assets needed for a beamed sail. But, this all boils down to this - pinnacle of space exploration being beam sail = b-o-o-o-r-i-n-g BTW I lied about my previous post being my last.

Firstly, the iron – An Iron will radiate, conduct and convect away every joule of energy that’s put into it that takes it above ambient temperatures – the *important* question is; what’s the equilibrium temperature? Now, you solar collector is NOT just going to be a graphene panel. There will be different materials involved and all (though there might not be many, but one is enough to this to be valid) these materials will have different coefficients of thermal expansion which is why passive cooling over a huge area ain’t an option in a *hot* environment, and making it in NEO and then shipping it to NSO is problematical. Not saying impossible, but why make a rod for your back when you’ve got another million-and-one problems to solve and only 50 years to do it in J Their orbital position is a very minor concern though but I maintain moving them closer to the sun is a bigger technical challenge than bigger collectors. No I didn’t forget about the unlimited budget, but having spent 20 years in product development of one kind or another I can you the single most important resource is people. Throwing money at projects only gets you so far – you can get nine women pregnant but that doesn’t mean you’ll get a baby in a month (as the saying goes). There simply aren’t enough skilled warm bodies to complete this project within the 50 year time-frame without getting silly. I really don’t think you’re fully appreciating the scope of the project. It took 16 years to develop the Airbus a380 at a cost of 11 billion Euroes. Doubling the budget wouldn’t drop the time to 9 years. Ten times the budget wouldn’t equal an 18 month development phase. It just doesn’t work that. That’s ONE aircraft (yes, I realise a lot of development was the assembly line – but the same applies to the fleet of spacecraft you’re going to need to loft the phase 1 equipment into orbit). Now, typically when someone says in X years time it’ll technically possible to build Z I would normally interpret that as meaning that by X date we’ll have Y technology which we can put together to build Z and not – If we sequester a not inconsequential percentage of the scientific and engineering resource on Earth for the next 5 decades we could do this. Hell, think of the technical challenge of the targeting system alone!?! Trying to shine a laser onto a target a few kilometres across at a range of 3 light months could absorb thousands of man years of development time. Developing something like a continuous 10gigawatt laser could run into millions, if not 10s of millions of man years. Actually building one that can run for months at time is just the FIRST step – then you’ve got to figure out how to build it in such a way that it can either be built in nice neat modules and assembled by people wearing spacesuits. If these figures sound outlandish I would point to the truck project going on around me at the moment – which is principally driven by the new European emission regulations. In the department I work in it’s taken approximately 300 man years of work. That one department in one company (numerous external suppliers have been effected as well) and doesn’t include the work that’s gone out sourcing new suppliers and outfitting the assembly line for the new truck model. So I could confidently double that figure – and that’s just to meet a new regulation and make some incremental developments to a well-established product that is, essentially 75% unchanged from the previous version. The bottom line is this, I’m not objecting to the idea as such but the 50 year time-frame is silly – talking about unlimited budgets and huge manpower, you might as well talk about magic wands. We *might* be able to start in 50 years. I’ll be surprised if asteroid mining isn’t in its early stages by then. So the very start of the infrastructure for this kind of project will be in place and resources in space will be starting to become more accessible. Whilst NASA may indeed state that this is the most realistic method of intersteller travel with conceivable technology that doesn’t mean it’s the most practical in game terms, and frankly, gameplay is FAR more important than physics. The scale of the task in-game is too big to go for something that’s vaguely realistic and so something considerably scaled down would be implemented. Physics would be fudged – just as almost every other aspect of the game goes. The planets are far too dense and too close together. Kerbol is too small to ignite into a star. Laythe has liquid water on its surface! All these are VERY unrealistic and yet NONE of them wreck the same and therefor prove you can take considerable liberties with physics and still wind up with something that *feels* realistic. Intersteller travel taking years is going to break the game as the travel times won’t fit with the in-system game. Remember, we’re not talking about getting to just the next system, but the one after that and then the one after that – and people calling for just a higher warp clearly don’t understand that you’re unlikely to be able to just “park†your whole space program for years at a time – it will likely need constant management. So you could be looking at dozens upon dozens of hours of gameplay before your very first probe arrives in the next system and begin its actual mission – and in intersteller terms this is like launching your first satellite into orbit around Kerbin. So, sorry, I see and FTL system, with travel time in weeks or months, that doesn’t work in-system (or just doesn’t allow you to target planets – only stars) as being the only practical solution to taking fun and interesting gameplay beyond the Kerbol system. Realism be damned. And that's pretty much my last word on this particular sub-topic. Really don't have the time go this in-depth any more.

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!

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.

I'm, glad you're enjoying yourself. I am too. 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.) 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. No? Really? Believe it or not I took that into account. I still think 1000 tonnes is low for this size of mission. Yup, still feeling I'm in the ballpark. I notice you're not giving an estimate. So what? Manned missions are all that count. 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. 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. Don't care about the unmanned portion of the mission, but we'll go with it - it's equally impractical. Are all your Kerbal mission unmanned? Why not? 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 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. This is going to be one fricking HUGE radiator. I'm considering crunching the numbers just for a laugh. 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? There are more sources than Wikipedia. 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?

This'll be using a definition of condescension that I am unaware of. Now that is reasonably condescending. But fair's fair. Which suffers from Problem No2 - it breaks the in-system game. If you have Orion why would you bother using anything else for moving around between planets? No more worrying about Hohmann transfers - just point at your destination and go.

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.

I was actually making a joke. Obviously, not one of my best.

Not pleased. I want a multi-star system AND other star systems

Ok, put your toys back in your pram and take a deep breath. Now, that picture in your head of how you think it would work? Yeah, it probably won't work anything like that. Like most simple answers, this one has problems as I've explained elsewhere, but I'll explain it again. Any conventional propulsion system that makes getting to another star feasible will make moving around WITHIN the system trivial. Consider your above numbers; 60 km/s - Assuming a round trip suggests a ship with 240,000 m/s of dV. What's the maximum at the moment? 10,000 m/s ish? Further compounding the problem. A ship capable of achieving 1% the speed of light and making a round trip will have a dv of 12,000,000m/s - a thousand times the current maximum. Getting from Kerbal to Jool and back will be like popping down the chemists. A warp drive that only works once you're outside the local star's gravity well and can propel a ship at a few multiples of the speed of light in a compressed universe allows the game to preserve the difficulties involved in moving around within a star system but still allow people to expand outwards to other systems. Well, assuming anti-matter entered the game I imagine it would work the same as any other fuel - available in any quantity your wallet can accomodate.

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. 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.

They've yet to create a single stage to orbit vehicle either.

And how is physics spelled in Spanish? Hardly, the "scientific method" dates from the 17th century. Nonesense: “There is no reason anyone would want a computer in their home.† Ken Olson, president, chairman and founder of Digital Equipment Corp. (DEC), maker of big business mainframe computers, arguing against the PC in 1977. “We will never make a 32 bit operating system.† Bill Gates “There is not the slightest indication that nuclear energy will ever be obtainable. It would mean that the atom would have to be shattered at will.† Albert Einstein, 1932 Humans will never stop saying stupid things. Doubtful dude (note, I'm not saying impossible). The energy requirements are ridiculous. Seriously, stupidly, huge. And we just don't have the power generating capability. If you want to tell me, then I'll listen, but I've just run through the numbers and they were bigger than I thought, so be prepared to be shot down - but I'll gladly listen. Personally I doubt solar sails will ever be used, but that's just because I firmly believe the warp drive is possible. the universe doesn't make sense if it isn't

And this is a really good point. ANY technology that comes into the game that allows travel between stars is going to be well within the realms of Sci-fi. Be it Bussard collectors, fusion drives, hibernation and whatever, going the extra few inches to an alcubierre drive doesn't seem like too much of a stretch.

We appear to have arrived on the same page

If you're running mission at a time I'm not surprised you're up to 40 years. When I was running my *campaign* I had a fairly well developed infrastructure that stretched from Duna to Jool completed in less than 5 years of game time, but I had numerous missions running simultaneously, and of course, there was no economy to worry about. I'm telling you right now, putting everything on hold for 10 years is COMPLETELY unreasonable and far more stupid as a game mechanic than any *magic* propulsion system. Well personally I've never assumed they meant some kind of instantaneous propulsion system as that wouldn't make any kind of sense and really wouldn't fit with the game. NOW the Kerbals live forever, but you're assuming there's not going to be any life support mechanic in the future, which would be more unrealistic than any *magic* click you're there drive. Expect to be making supply runs, need hydroponics and Kerbals dying if you run out of something important, whilst you're sitting waiting for 10 years to pass in high warp.

You planning on hibernating your entire space program? By the time you launch your intersteller ship you're likely going to have dozens, it not hundreds of Kerbals in space. Various bases, mining outposts etc etc. You planning on putting all that interesting stuff on hold for several decades of game time to watch one ship fly through empty space? Who said it'd be done with one click? Oh, you. So what? An Alcubierre drive is an FTL system. But what do you do about the other 99% of your space program? Are you seriously telling me an FTL system is more unrealistic than putting an entire space program on hold for several decades?