Cad
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I agree it would be a big, long term project. Doesn't mean it's not something we should attempt.
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The Astronomy Thread
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I agree it would be a big, long term project. Doesn't mean it's not something we should attempt.
Tuco
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I feel like any interstellar project we start now will create a space vehicle that will be passed before it reaches the star by one we'd create 100 years from now . And that 100 year later space vehicle will get passed by one we create 200 years from now. And that one will be passed by one we create 300 years from now. And so on until 2000 years from now we use a wormhole to get to that star and tell the alien civilization we meet there, "Uhh, we've got a few bits of space junk we hurled at you. We're not sure where it is, where it'll hit or when it'll come, sorry.".
I wouldn't mind seeing a project that sent a seed ship to another star, but only if the technology is there already (it isn't). That would cover humanity's ass if our civilization was wiped out. I'm sure the people (if they exist) on that seed ship would be annoyed when they land in Disneyworld 2: Centauri Edition 20k years later, but it'd still be a good backup.
A simple probe on the other hand, if it lands 10k years after humanity is wiped out, who cares that we sent it?
I wouldn't mind seeing a project that sent a seed ship to another star, but only if the technology is there already (it isn't). That would cover humanity's ass if our civilization was wiped out. I'm sure the people (if they exist) on that seed ship would be annoyed when they land in Disneyworld 2: Centauri Edition 20k years later, but it'd still be a good backup.
A simple probe on the other hand, if it lands 10k years after humanity is wiped out, who cares that we sent it?
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Cad
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How fast could a nuclear pulse powered ship get there? Say we launched it out to one of the lagrange points by chemical rocket and then assembled it in space from multiple launches, then lit it up well out of earth range for safety...
Big project, not ridiculous?
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iannis
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it's a real tricky thing. we're at the point right now where it's a valid argument to say, "With the rate at which technology is progressing, if we wait for ten or twenty years to begin then we will finish more quickly". And that's a true statement. Obviously the problem is that when we do reach a plateau the valid argument will be "we need to break through this plateau before we consider the pursuit of trivialities"
I'd like to see it, too. But it's like the golden record or SETI. It's almost entirely, but not entirely, an idealistic pursuit.
I'd like to see it, too. But it's like the golden record or SETI. It's almost entirely, but not entirely, an idealistic pursuit.
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iannis
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Heinlein had a few pages buried in one of his mars books talking about the mathematics of it. The math is actually fairly trivial on that point.
The application of constant thrust is a truly magical thing. But... rocket problem. Right now to apply a constant thrust you require propellant. Propellant requires mass, mass requires force to be moved, descending spiral.
I really hope the EM drive isn't complete bullshit. If there is a way to convert electrical or magnetic energy directly into kinetic energy, and to direct the output, it's no exaggeration to say that it opens up the stars.
The application of constant thrust is a truly magical thing. But... rocket problem. Right now to apply a constant thrust you require propellant. Propellant requires mass, mass requires force to be moved, descending spiral.
I really hope the EM drive isn't complete bullshit. If there is a way to convert electrical or magnetic energy directly into kinetic energy, and to direct the output, it's no exaggeration to say that it opens up the stars.
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Cad
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Depending on the thrust per power it produces it would completely revolutionize all forms of travel
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Tuco
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No idea, but I'm willing to make a 100 year avatar bet the answer to "how fast" is "slower than what we'll have in 100 years, or we'll all be dead and it doesn't matter".
I wouldn't count on the EMDrive, it's probably bullshit. A few groups have independently found thrust, but zero groups have yet come out with a repeatable test system that they will let others test and verify. This combined with nobody being able to explain the physics in a defensible manner (and a lot of the proponents explaining the physics in an indefensible manner, as in, spouting bullshit that's easily falsifiable) makes the whole thing sound like bullshit.
There is a publication coming later this year on it though.
Peer-Reviewed Paper On EmDrive To Be Published In December
The drive allegedly has 1.2mN / Kw thrust, from this post by Dr. Rodal.
This is 0.1% as much as Cannae bullshits, 1% as much as Shawyer bullshits, 20% as much as the best Eagleworks result and 0.1% as much as what Prof. Juan Yang found.
However, a photon 'rocket' has 0.003336 mN/kW, so it's like 300 times better than a flashlight rocket.
Experimental Results - EM Drive
I think the hope is that we can figure out the tech and bring it up to the 1N/kW level. Which would mean that the power required to heat your burrito would produce about as much force as you feel when you hold that burrito in your hand on earth. This would be enough to get to Mars.
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Cad
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Mars would be thinking small if you had a nuclear electric propulsion that you could run 100% of the time...
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iannis
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It's enough to get you anywhere, honestly. Within credible timeframes even. I mean you're still talking about decades to centuries. But for the distances involved, that's credible.
I think the real trick then, with probes, is how do you communicate with them? You don't. Nothing that we're using right now will work. It'll have to be a round trip, and it'll have to be completely autonomous.
So we need to get to workin on that there WATSON.
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Cad
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My shitty back of the napkin calculations using an S8G reactor are:
Reactor weight: 2750 tons (approximately 5 million pounds). Reactor power: 220MW
Figure the spaceship has to be twice as big as the reactor. This gives you a 10 million lb spaceship. With 220MW on tap you could produce 220,000N at 1N/kW.
This gives you a .05m/s^2 acceleration.
To reach .2c (215 850 570 km/h) would take your probe 18.3 years. Thats still kind of shitty but "doable". I wonder if they could develop a higher power/weight reactor for space.
Reactor weight: 2750 tons (approximately 5 million pounds). Reactor power: 220MW
Figure the spaceship has to be twice as big as the reactor. This gives you a 10 million lb spaceship. With 220MW on tap you could produce 220,000N at 1N/kW.
This gives you a .05m/s^2 acceleration.
To reach .2c (215 850 570 km/h) would take your probe 18.3 years. Thats still kind of shitty but "doable". I wonder if they could develop a higher power/weight reactor for space.
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Cad
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Yea I have no idea. I don't know that they've ever had to dissipate that kind of heat in space before.
How Does a Spacecraft Dissipate Heat?
If vacuum is used in thermos bottles to keep heat or cold from leaving, how can a spacecraft get rid of any excess heat or cold in the vacuum of space?
There are three ways of transferring heat: convective, diffusive, and radiative.
- Convection transfers heat by moving matter, usually a gas, around. A fan blowing on you is convective cooling.
- Diffusion is the transfer of heat through contact, like putting your hand on an ice cube.
- Radiative transfer uses photons (light or infrared photons) to transfer heat.
Dr. Eric Christian
Dissipating a full power nuclear reactors worth of heat? Probably need very large thermal radiators. This would complicate the design I'm sure.
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iannis
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How about them carbon nanotubes? They're supposedly really good at conducting heat. You could trail a cloud of those bitches.
I mean i'm out of my depth. But it seems like there might be practical low mass engineering solutions to that problem. Maybe.
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Tripamang
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Starshot plans on sending small probes to other systems in the near future provided they get all their funding together. I'm pretty sure they'll get their little probes up to 20% of the speed of light using a high powered laser and a light sail which makes for roughly a 20 year journey to Alpha Centauri. The probes never slow down, they'll just keep on going through the system though. Since the probes only weigh a few grams and are cheap produce they can in theory send a continuous stream of them at other systems to get all kinds of views.
Breakthrough Initiatives
On the topic of chemical rockets, don't those top out at fairly low numbers in terms of max speed? I always thought your max speed was limited to how quickly the exhaust leaves the rocket.
Breakthrough Initiatives
On the topic of chemical rockets, don't those top out at fairly low numbers in terms of max speed? I always thought your max speed was limited to how quickly the exhaust leaves the rocket.
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Cad
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They are, none of the functional drives that we have right now will get us to another star in less than like 5000 years or something stupid.
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iannis
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But how are they going to get any meaningful information back from the probes?
It says "beaming home". I thought that we can't make a focused enough laser for that to approach practical, and our traditional EM communications are subject to too much deterioration to be useful at that distance.
Obviously one of these two things I believe are not true.
It says "beaming home". I thought that we can't make a focused enough laser for that to approach practical, and our traditional EM communications are subject to too much deterioration to be useful at that distance.
Obviously one of these two things I believe are not true.
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Cad
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Inverse square law is an issue but I think thats an engineering problem. Obviously we can detect radio signals from many many light years away.
This would also be entertaining
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iannis
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Max speed tops out at how long you can apply thrust.
I mean we're not talking about extreme ranges where things start to get weird. If we can hit .1 or .2c that is significantly faster than anything we've done yet. Like many many decimal places significant.
I mean we're not talking about extreme ranges where things start to get weird. If we can hit .1 or .2c that is significantly faster than anything we've done yet. Like many many decimal places significant.
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Tuco
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The advantage of carbon nanotubes would be we'd effectively create those squids from the Matrix, or some kind of jellyfish ship. The idea of space ships being small ringed modules surrounded by massive clouds of nanotubes is too silly to work!
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