Newtonian ships or not?.

[Baron Munchausen]

Originally posted by narf poit chez BOOM:
your post stired up a thought...what if the heat generated by interstellar dust was used to pre-heat the reaction mass?

A fascinating thought. But any 'reaction' drive suitable for interstellar travel is going to need to have a very high impulse (thrust per weight units of fuel) ratio. This means something with very high energy like a fusion reactor with an opening pointing out the back. It sounds good in theory to run your coolant around the spaceship skin and then route it to some sort of 'converter' to preheat the fuel -- but how are you going to convert plain old radiant heat carried by a 'coolant' medium into the extremely intense sort of energy needed for fusion reactions? A pelet of fuel (probably hydrogen in a little glass 'bubble') has to be heated to thousands of degrees in a tiny fraction of a second -- probably by lasers. If this extreme conVersion can be done at all it looks likely to be very involved and complex. And once you figure out all the tricks necessary to do this, are you gonna have any space left in your ship for cargo between all those heat-exchanger coils and electrical generators and what not? So though it sounds good on its face I wonder if it can be done in practice.

This sort of reminds me of the idea of putting generators on the wheels of an electric car. Yeah, it should work (and some electric cars do recover a small amount of energy this way) but the inherent inefficiencies put some pretty steep limits on its effectiveness.

Maybe there are simpler ways to do it? Do thermocouples actually 'use up' energy and reduce their heat levels by generating electricity? A ship with a skin made of thermocouples is an interesting concept. Peltiers reduce temperature by moving the heat around but you still have to dispose of it somewhere, somehow and the Peltier effect USES energy and creates more heat.

It's a very difficult problem.

[ March 27, 2004, 04:02: Message edited by: Baron Munchausen ]

[Baron Munchausen]

Originally posted by Randallw:

quote:

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Originally posted by Baron Munchausen:
In order to 'maneuver like a plane' there would have to be an atmosphere for wings to work on. Or alternatively, you need to be moving at a signifigant fraction of the speed of light in order to get similar effects from the 'vacuum' of space

Ha, I knew saying plane, someone would think of spaceships with wings . Let me use examples to show what I mean. Hard Science ship, a ship that accelerates at a fraction of c and needs to do stuff like turn halfway through the journet to decelerate. Pulp ships, the good old Star Wars or Star trek ship. Disregarding their faster than light speed, when they move at sublight speed they can turn whenever they want and stop suddenly without regard to inertia.

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Planes don't move without inertia. You are talking about something completely unknown and probably impossible, but yes we do see that in many shows like Star Trek. This is 'simplified' SciFi for the sake of making a short and simple television show or movie.

[President_Elect_Shang]

FTL via worm holes:
http://www.quantonics.com/Faster_Tha..._Discover.html

Good info:
http://www.lerc.nasa.gov/WWW/PAO/warp.htm

There should also be an article in the London Sunday Times on 4 Jan 2000 in which some US scientists managed to accelerate light pulses past the speed of light. I would have loved to include the link but the London Times charges for its archives. You guys just aren�t that important for me to start forking out my cash! Anyway I feel that one day we will have starships able to move faster than light. I am not saying that a human crew will be on it, maybe robots.

[Phoenix-D]

Actually it is possible to go past the speed of light, just not the speed of light -in a vaccum-. IIRC the 2000 experiment didn't break c, just the speed of light elsewhere.

There's actually a specific type of radiation that you get when you break the local speed of light, much like the shock waves when you break the speed of sound.

cherenkov radiation

[narf poit chez BOOM]

Well, like I've said before, just maybe not on here, people once thought 60 miles an hour would tear the skin off your face. They thought the speed of sound was unbreakable. Well, I don't know how many other things we've done have been labeled impossible, but probably a lot.

I don't truly beleive that impossible is the right word...I think 'non-existant action/direction' is better, that is, if you think of any action we take as an action/direction, there are places you can go and places you can't and if you can't, it's not because you're blocked, it's because that action/direction doesn't exist.

Also, the nature of light itself lends some credence to the theory of holes? in or around or something the speed of light barrier.

[capnq]

A ship with a skin made of thermocouples is an interesting concept.

The main problem is that a typical thermocouple only has an output of tens of microvolts. Other means of generating electricity are more efficient.

[Roanon]

Originally posted by JurijD:
you could colonize the entire galaxy in a couple 100-thousand years...

100 to 1,000 years? 100,000 years? Oh well, what are a few powers of ten among friends...

[geoschmo]

Originally posted by JurijD:
so the real question is: why hasn�t anyone done it yet) how come I don�t have a weird little green man for my neighbour... no wait I do.. at least the weird part

There are many possible answers to this question.

It's possible we are alone, although I think it's very unlikely.

It's possible that there are others out there, but none as advanced as us. Again, I think it's an unlikely possibility.

The most likely possibility I suspect is that your assumtions are overly optimistic. It may in fact be much much harder then you you think to travel between the stars. Without some major breakthrough that we can't predict or plan for, it's very unlikely that we will progress in 100 years to any sort of technology that will allow for reasonable travel times. If it takes centuries to get to the nearest star, then it becomes much more difficult to build ships that can stay together long enough to get us there alive. We aren't even sure yet how will overcome the damage to our bodies living in space for the few months it takes to get to Mars. Not even considering the prospect of our ships wearing out.

Assuming we can get there, you are wanting the people you sent to get right to work building another ship. This of course will have to be built entirely from local materials. Which means a lot of infrastructure work building factories and extracting resources, on top of whatever needs to be done just to survive in their new environment. What will be the impetus driving the colonists to send ships to another system? Wouldn't many of them be more interested in exploring their new planet and system? Making a life for themselves?

I am sure eventually they will get to the point of sending out another ship, but 100 years seems very soon to me.

If we do not make any sort of tremendous breakthrough in travel speed, I think it will be a very long time before we leave our own star system. For one main reason, why go? If you overcome the problems with living in space for long periods of time, and can build the size of ships that would be neccesary to send thousands of people to Barnards Star, why not build an L5 colony instead? Or a domed city on Mars, or an undersea city on Titan? There are a lot of interesting places to go right here in our own solar system. And there's lot's of room to expand. It will be quite a while before we run out of room. You could get your fill of exploring new and interesting places, and still be just a few months or years from mother earth.

[geoschmo]

Originally posted by Roanon:

quote:

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Originally posted by JurijD:
you could colonize the entire galaxy in a couple 100-thousand years...

100 to 1,000 years? 100,000 years? Oh well, what are a few powers of ten among friends...

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Actually there's not much difference in this case. If is his basic assumtion is correct, that a new colony could send a new colony ship in 100 years, and additionally we assume that it takes an average of 100 years for the each colony ship to reach it's new home, we could colonize the entire galaxy in less then 4000 years.

That's about the length of recorded human history. But even if he meant it would take 100,000 years, considering the age of the galaxy we should be seeing someone out there. So either we are alone, or they don't want us to know they are there, or it's a lot harder then we think to get around out there.

Geoschmo

[Baron Munchausen]

Not only travel but simple survival in space might be more difficult than we realize. It's amazing to think how little we really know about space travel. Only the dozen or so men sent to the Moon in the 1960s and early 1970s have ever been outside of the Earth's magnetic field. And that only for a few days. Everything else we think we 'know' about space travel is speculation from SciFi.

Just about every single lunar astronaut had some sort of psychiatric problems when they returned. You could easily assign this to 'stress' of course. They had been on a very dangerous mission (think of the creaky little tin-can space ships they traveled in!) and were trained very rigorously, so being released from that pressure and sitting back and realizing what a dangerous thing they had done could have had an effect on their mental stability.

But we don't have access to their medical records. Only the US Government has access to all of their medical records. I've seen some NASA people post on other discussion Boards that the 'real reason' we haven't returned to the Moon is classified. In other words, it was not simply budget reductions. There was a real reason that the Moon missions stopped. Could they have noticed something in the medical information about the returned astronauts? Were they affected in unexpected ways? Maybe life here on Earth has some important relationship with the magnetic field and leaving the earth's magnetic field unbalances something in our biology? Changing your home might not be as simple as jumping from one rock to another in space. Life processes could be dependent on other factors that we haven't figured out yet. We may be part of this planet in a way that we cannot change.

[ March 28, 2004, 00:30: Message edited by: Baron Munchausen ]